Outside his political base, Poilievre’s populist pitch is a harder sell.

Three more parties, all projected to secure small numbers of seats in the country’s parliament, the House of Commons, are in the fray: the left-wing New Democratic Party, the Greens, and the Bloc Quebecois, which is focused on gaining sovereignty for Quebec.

Just three months ago, the Conservatives had been leading polls by more than 25 percentage points and Mr. Poilievre was all but certain to become Canada’s next prime minister. Justin Trudeau and the Liberals had led the country for a decade, becoming increasingly unpopular.

But Mr. Trudeau’s resignation in March and Mr. Trump’s tariffs and sovereignty threats against Canada upended the race. With Mr. Carney as the party leader and prime minister, the Liberals rapidly gained support as the ones to better handle Mr. Trump.

In Canada’s parliamentary system, voters choose who they want to represent their electoral district, known in Canada as a riding; the candidate who has the most votes wins, and the party that has the most seats becomes the ruling government, even if they do not control the majority. There are 343 seats in parliament.

But the two leaders vying to become Canada’s next prime minister are central to the choice Canadians will be making on Monday, and they offer different personalities, experiences and visions for the nation at a critical juncture.

Here’s what else to know:

• The incumbent: Mr. Carney, 60, replaced Mr. Trudeau as prime minister just a month ago. He is a former central banker and executive with a global career. A dedicated centrist who has spent a lifetime in rarefied high-power circles, he has built his pitch as an anti-Trump, vowing to devote his financial expertise to improving his country’s economy and shielding it from Mr. Trump’s tariffs and annexation threats.

• The challenger: Mr. Poilievre, 45, is a career politician who supports deregulation and a smaller federal government. His tonal and ideological similarities to Mr. Trump — he denounces “woke ideology,” wants to defund the national broadcaster and slash foreign aid — have turned some voters away who see him as too similar to Mr. Trump at a time when the U.S. president is seen as an enemy of Canada.

• Closing times: Polls opened in a staggered manner to make vote counting easier across the vast country’s six time zones. Most will close at 9:30 p.m. Eastern time.

• Results: Ballots are counted by hand, not machines. Results should be known late Monday night. The New York Times will provide live results coverage with detailed information about every district race.

• Choosing leaders: Party leaders were chosen by party members in earlier votes. In federal elections, voters do not vote for Canada’s leader, as they might in a presidential system.

He also called Canada “a beautiful landmass” and referred to the border between the two countries as an “artificially drawn line from many years ago.”

Since taking office, Mr. Trump has repeatedly said Canada “doesn’t make sense” as a country but should just join the United States, threatening Canada’s sovereignty.

His tariffs against America’s closest ally and trading partner have pushed Canada closer to a recession, and his constant refrain about making Canada part of the United States have upended the political balance of power, boosting the previously moribund Liberal Party and hobbling the once dominant Conservatives.

He had made similar remarks questioning the permanence of the border between the two countries to former Prime Minister Justin Trudeau, putting Canada’s leadership on alert that the president of the United States was serious about taking over Canada.

Observers struggled to interpret Mr. Trump’s Monday missive.

Some felt it was veiled support for Pierre Poilievre, the Conservative Party leader, who is seen as a close ideological ally of Mr. Trump and has been criticized for being too Trump-like by many voters.

Others thought Mr. Trump’s post favored — perhaps inadvertently — Mark Carney, the current prime minister and Liberal leader, who’s shaped his campaign on an anti-Trump platform.

Whatever the case, one thing was clear: Mr. Trump is not giving up on his obsession with Canada, and the new government that emerges from Monday’s vote will need to deal with a leader intent on both hurting Canada’s economy with tariffs, and coveting its vast resources.

Mr. Trump’s post Monday was met with a swift rebuke by Mr. Poilievre.

“President Trump, stay out of our election,” the Conservative leader said on X.

“The only people who will decide the future of Canada are Canadians at the ballot box. Canada will always be proud, sovereign and independent and we will NEVER be the 51st state. Today Canadians can vote for change so we can strengthen our country, stand on our own two feet and stand up to America from a position of strength,” he added.

Mr. Carney also shared a post that reinforced Canadians’ independence and agency over who’s in charge in their homeland, but did not mention Mr. Trump, posting a video in which he said, “This is Canada, and we decide what happens here.”

He railed against an economy that he said was “a transfer of wealth from the have-nots to the have-yachts.” He whipped up thunderous applause with his vow to “cut foreign aid to dictators, terrorists and global bureaucracies, to bring our money home.”

He pledged that Canada’s beefed-up armed forces would be “guided by a warrior culture, not a woke culture.” His promise to eliminate the CBC, the public broadcaster he has accused of liberal bias, drew some of the most sustained applause.

“I love you, too,” Mr. Poilievre said after a long pause and a sip of water. “I love you, I love you, I love this province.”

Alberta, the oil-rich province in Western Canada, is the birthplace both of Mr. Poilievre, 45, and the right-wing populist movement that has come to dominate Canada’s Conservative Party.

Mr. Poilievre’s message of “common sense” against a purportedly corrupt elite resonates the most in Alberta, along with neighboring Saskatchewan, where support is also highest in Canada for the man who has upended its political landscape: President Trump.

But Mr. Poilievre’s deep ties to Alberta and its brand of conservatism are complicating his efforts to win voters in battleground provinces, especially Ontario and Quebec, ahead of the April 28 election.

In Ontario, the province with the largest number of voters, moderate conservatives allied with the provincial government have chosen not to help Mr. Poilievre’s campaign and are working with Mr. Carney’s government to challenge the tariffs by the Trump administration.

A high-ranking conservative official in Ontario said publicly that Mr. Poilievre was “too much like Trump.”

Now that most Canadians view Mr. Trump, who has vowed to annex Canada, as the greatest threat facing their country, being too much like the American president is considered a liability — except perhaps among some Conservatives.

“The difficulty for Mr. Poilievre in going beyond his base and becoming the strongest defender of Canada is his association with Trump,” Jean-Marc Léger, the president and chief executive of the firm, said in an interview.

Where do I vote?

You’ll need to find the polling station associated with your address. You can find your station on Canada’s election website or by calling 1-800-463-6868.

When are polling places open?

Polls are open for 12 hours across the country, and voting hours vary by time zone.

In the Pacific time zone polls are open from 7 a.m. to 7 p.m., and in the Mountain time zone, polling stations are open from 7:30 a.m. to 7:30 p.m.

In the Atlantic, Central, and Newfoundland time zones, polls are open from 8:30 a.m. to 8:30 p.m.

In the Eastern time zone, polls are open from 9:30 a.m. to 9:30 p.m.

What happens if I’m in line when the polling station closes?

Stay in line: Anyone already in line will be able to cast their ballot.

What do I need to bring to the polling place?

Bring your voting card that you received in the mail, and a form of identification with your name. Here’s a list of acceptable forms of government issued identification.

What if I didn’t register to vote?

You can still register at your polling station on Monday. Bring an identification card that shows your current address.

If you recently moved , you can provide a handful of documents to prove your new place of residence.

But they were perfect fodder for Canada Proud, a right-wing Facebook page with more than 620,000 followers. For days, Canada Proud posted about the images, including in paid ads that repeatedly said Mr. Carney had been “hanging out with sex traffickers.”

This type of online content — hyperpartisan and often veering into misinformation — has become a staple in the Facebook and Instagram feeds of Canadians in the run-up to the election. While such posts have become familiar in political campaigns everywhere, the content is especially prominent in Canada during its first-in-the-world, long-term news ban on Facebook and Instagram.

Meta, which owns Facebook and Instagram, blocked news from its apps in Canada in 2023 after a new law required the social media giant to pay Canadian news publishers a tax for publishing their content. The ban applies to all news outlets irrespective of origin, including The New York Times.

Amid the news void, Canada Proud and dozens of other partisan pages are rising in popularity on Facebook and Instagram before the election. At the same time, cryptocurrency scams and ads that mimic legitimate news sources have proliferated on the platforms. Yet few voters are aware of this shift, with research showing that only one in five Canadians knows that news has been blocked on Facebook and Instagram feeds.

The result is a “continued spiral” for Canada’s online ecosystem toward disinformation and division, said Aengus Bridgman, director of the Media Ecosystem Observatory, a Canadian project that has studied social media during the election.

Meta’s decision has left Canadians “more vulnerable to generative A.I., fake news websites and less likely to encounter ideas and facts that challenge their worldviews,” Dr. Bridgman added.

In a statement, a Meta spokesman said the company had been “forced to make the difficult business decision to end the availability of news to comply with the law.” That could change if the law is reversed, he said. Paying publishers would most likely cost Meta, which generated $164.5 billion in revenue last year, 62 million Canadian dollars a year, or about $44 million.

Canada Proud, which is now one of the most popular political Facebook pages in Canada and has more followers than the country’s major parties, has emerged as a particularly potent weapon aimed at the Liberal Party and Mr. Carney.

Since Mr. Carney called last month for a snap election, Canada Proud has averaged nearly 200,000 engagements a day, rivaling the engagements of official Facebook accounts for the major political party leaders, according to an analysis by The Times. Since January, Canada Proud has had more than nine million engagements on its posts and its videos have been viewed nearly 60 million times, the analysis found.

Trump’s Trade War

While Mr. Trump pulled back from his initial threat of tariffs on everything imported from Canada, he has imposed several measures that hit key sectors of Canada’s economy: a 25 percent tariff on automobiles, aluminum and steel, and a similar one on Canadian exports that do not qualify as North American goods under the United States-Mexico-Canada Agreement, which he signed during his first term in office. An auto parts tariff of 25 percent is scheduled to take effect on Saturday.

Last week, Mr. Trump suggested that the automobile tariffs, which are reduced based on their U.S.-made content, could be increased. He offered no specifics.

Autos and auto parts are Canada’s largest exports to the United States, outside oil and gas.

Canada Hits Back

Under Mr. Trudeau, Canada placed retaliatory tariffs on U.S. goods coming into Canada that are expected to generate 30 billion Canadian dollars, about $22 billion, in revenue over a year.

After becoming prime minister in March, Mark Carney imposed an additional 8 billion Canadian dollars, about $5.7 billion, in tariffs, including a 25 percent levy on autos made in the United States — but not on auto parts. Automakers with assembly lines in Canada will still largely be able to bring in American-made cars of those brands duty free.

The Canadian public has responded, too. Travel to the United States has declined sharply. Government-owned liquor stores in several provinces removed American beer, wine and whiskey from their shelves. As calls for boycotts of American products grew, Canadian manufacturers hurried to adorn their packaging with maple leaves and Canadian flags.

How to Handle Trump

Both Mr. Carney, who also succeeded Mr. Trudeau as the Liberal Party leader, and Pierre Poilievre, the Conservative leader and the other major contender in the election, have adopted a hard line when it comes to the U.S. president.

In a conversation with Mr. Trump, in March, Mr. Carney said that the president had agreed to begin economic and security negotiations with whoever emerges as prime minister. During those talks, Mr. Carney said during a televised debate, “the starting point has to be one of strength.”

He added: “It has to show that we have control of our own economic destiny.”

Throughout the campaign, Mr. Carney, who was a governor of the Bank of Canada and later of the Bank of England, has sought to emphasize that his background in the financial world makes him the ideal candidate to tackle both Mr. Trump and the economic challenges his tariffs pose.

When asked how he will deal with Mr. Trump, Mr. Poilievre, a lifelong politician, usually responds by saying that he will first tackle what he views as problems the Liberals have created within Canada.

“I would cut taxes, red tape and approve our resource projects so that we can get our goods to market and bring home the jobs so we can stand up to President Trump from a position of strength,” he said during the debate.

The Crisis Will Probably Get Worse

Mr. Trump’s auto tariffs had an immediate impact. A factory in Windsor, Ontario, where Stellantis makes Chrysler minivans and Dodge muscle cars, was shut down for two weeks while the company considered its options. The association of auto parts makers said that its members had already laid off several thousand workers in Ontario.

There have also been a small number of layoffs in the steel industry.

The threatened tariff on auto parts may have a profound effect. Auto parts makers employ more people than the automakers’ assembly lines. Many parts companies are small, sometimes family-owned businesses without the financial resilience of multinational car manufacturers.

Economic Ideas, but Few Details

Both leaders, but Mr. Poilievre in particular, have promoted the construction of oil and gas pipelines to make it easier to ship fuel to Europe. They have not offered any specifics about what companies, if any, are interested in those projects or how they would be financed.

Mr. Poilievre also said he would accelerate environmental reviews and consultations with Indigenous groups for natural resource projects. Environmental groups and Indigenous leaders have criticized the proposal and questioned its legality.

For the auto sector, Mr. Carney has proposed to create an “all-in-Canada” system in which cars are assembled in Canada using Canadian parts made from Canadian steel and aluminum. He has not said how he would persuade automakers to go along with the plan.

Mr. Carney has also promised to set aside 2 billion Canadian dollars to help the auto industry adjust to U.S. tariffs and vowed that the money collected from retaliatory tariffs would be used to help companies and workers disrupted by the trade war. He has not specified what that help would involve.

“Because of the distribution of the vote nationally, there is a little bit of distortion, not unlike what you will see in the U.S. with the Electoral College,” said Sébastien Dallaire, the executive vice president for Eastern Canada for Leger, a major polling firm.

But, he added, “even if the national vote were to be tied, it would probably mean that the Liberals won more” seats in the House of Commons, allowing them to form a government and giving Mr. Carney a full term as prime minister.

Polls could also underestimate national support for the Conservative Party, led by Pierre Poilievre, but it still might not be enough to overcome the Liberals’ advantage.

The Conservative Party won the popular vote in the past two elections, but still lost to the Liberals both times. The Conservatives can poll well nationally, but still fall short because their support tends to be concentrated in a smaller number of parliamentary districts.

Conservatives have overwhelming support in the Western provinces of Saskatchewan and Alberta, but this amounts to relatively few seats because their populations are lower than provinces that are more competitive.

In Canada’s “first past the post” electoral system, in which the candidate who receives the most votes — but not necessarily a majority — wins, having a lower level of support in a higher number of districts is more of an advantage.

Polling in Ontario and Quebec, which have more seats than the rest of the country combined, shows a much stronger Liberal advantage. In Ontario, the Liberals have a seven percentage point lead on average, while in Quebec, it is closer to 15 percentage points.

Only a few months ago, a Liberal win in the election seemed extremely remote.

Canadians had soured on Prime Minister Justin Trudeau and his Liberal Party after a decade in power, and the Conservatives had a more than 20 percentage point lead in the polls.

But after President Trump launched a trade war against Canada and began threatening to annex the nation as America’s “51st state,” public sentiment began to turn. Once Mr. Carney replaced Mr. Trudeau as head of the party in March, the reversal of fortune gained momentum as voters saw Mr. Carney as the candidate most capable of taking on Mr. Trump.

Beyond the horse race, polling about the issues Canadians are most concerned about heading into Election Day has shifted, but it still suggests an advantage for Mr. Carney.

In recent weeks, surveys show that the focus on Mr. Trump has waned, while the economy and affordability have become more salient issues. Across various polls, Mr. Carney and the Liberal Party have had the advantage on U.S.-Canada relations.

But Mr. Carney, with his experience as the head of the central banks in Canada and Britain, is also well regarded on economic issues: A plurality of Canadians in a recent Abacus Data poll said the Liberal Party was best able to grow the economy.

At the start of the campaign, more Canadians said they were voting based on which party they felt would be best suited to taking on Mr. Trump, according to polling by Abacus Data. In more recent surveys, a majority of Canadians say they’re more interested in which party can deliver a change in the country’s direction.

But while a majority of voters who prioritize change favor the Conservatives, one in four still prefer the Liberals, according to Abacus, despite the party being in power for the past decade.

“That tells me that Mark Carney has done enough to signal and comfort those voters that he is a sufficient enough change from Justin Trudeau,” said David Coletto, the founder and chief executive of Abacus Data. “The way that he approaches both leadership and this campaign has been satisfying enough to people who might otherwise have wanted a change. That, I think, is why they’re holding onto the lead.”

Voters in Toronto had been vital to keeping Mr. Trudeau and the Liberals in power through three elections. So the loss of a Toronto district — held by a prominent Liberal for 28 years — to the Conservatives was a stunning blow and an omen of worse to come in a general election.

Now, with all 343 seats in the House of Commons to be filled in the general election, the 56 at stake in the loosely-defined Greater Toronto Area will likely determine who will steer Canada through a trade battle with the United States that could deal a devastating economic blow.

The Conservatives had been making inroads in the crucial Toronto area, with about 7 million people, before President Trump upended the electoral landscape by imposing tariffs on Canada.

The two leading contenders to become the country’s next leader are Prime Minister Mark Carney of the Liberals and Pierre Poilievre of the Conservatives.

These voters who could go in any direction

While the two dozen seats in Toronto have not been fertile ground for the Conservatives, despite the special election result, voters in the 32 districts in the fast growing communities surrounding the city are not particularly attached to either major party and are up for grabs.

“I wouldn’t say ideologically they’re overwhelmingly Conservative,” said David Coletto, the head of Abacus Data, a polling firm. “But that more leftist-center, or left-wing activist core we see in downtown urban centers — that doesn’t exist.”

In the past, Mr. Coletto said, many voters outside Toronto helped Liberals win federal elections, but would vote for candidates from conservative parties in Ontario’s provincial votes.

Underscoring the importance of the region to the overall result, Mr. Carney is expected to spend much of the final weekend of the campaign in the Greater Toronto Area.

Appealing to immigrant voters is important

Many ethnic communities, including some with a large number of recent immigrants, dominate some of the communities surrounding Toronto, from South Asians and Italians northwest of the city, to Chinese and other Asian communities to the northeast.

While immigrants cannot vote until they obtain citizenship, all major political parties have long concentrated on courting their communities.

A federal task force on intelligence and security threats to the election has said that India, China, Pakistan and Iran are likely targeting those communities with disinformation campaigns related to the election.

This week it said had discovered that China is seeking to turn Chinese-speaking Canadians against a Toronto-area Conservative candidate who is a critic of the limits on democracy in Hong Kong.

Dennis Pilon, a political scientist at York University in Toronto, said that some leaders of those ethnic groups can be important political influences.

The cost of living and house prices are concerns

The cost of living is a top concern for voters in communities outside Toronto, Mr. Coletto said, adding that many residents live in those ares largely because they cannot afford homes in the city or in nearby suburbs.

House prices in Toronto have risen by 44 percent since 2020.

Until the beginning of this year, that worked in favor of Mr. Poilievre, who regularly blamed Mr. Trudeau for inflation and rising house prices.

And many voters, Professor Pilon said, had simply tired of the Liberals after a decade in power and a sense that the country was headed in the wrong directly.

Both parties have promised to help financially-strapped Canadians by providing tax breaks for some home buyers.

Trump’s tariffs, a new leader bring a reversal

Mr. Coletto said that his polling shows the Liberal now lead by 15 percentage points in Toronto and by eight percentage points in the broader Greater Toronto Area.

The Liberals have gained strength in recent weeks, while the Conservatives and some smaller parties have lost ground, and a significant factor has been Mr. Trump’s economic attacks against Canada and his talk of annexing the country.

Polls have consistently shown that Canadians believe that Mr. Carney, a former central banker with experience dealing with past financial crises, can do a better job than Mr. Poilievre in dealing with Mr. Trump.

U.S. tariffs, including on vehicles and auto parts, may have a disproportionate effect on the Greater Toronto Area, which is home to many auto parts makers, as well as vehicle assembly plants of General Motors and Stellantis, the owner of Chrysler.

The tariffs Mr. Trump has applied on its neighbor may play a key role in determining who will capture this deep well of Canadian voters, analysts said.

To win a national election without doing well in greater Toronto, “you need to win everything but” that region, Mr. Coletto said. “That’s impossible in a country is diverse and different as Canada.”

Pierre Poilievre, 45, the Conservative Party leader, has been a politician for most of his adult life and is well known to voters, having meticulously curated his agenda, talking points and image.

Two other candidates are vying to maintain their parties’ representation in Parliament: Jagmeet Singh of the New Democrats, a leftist party that has focused much of its campaign on health care, and Yves-François Blanchet of the Bloc Québécois, which runs candidates only in Quebec. But Mr. Poilievre and Mr. Carney are widely acknowledged to be the only two who can gain enough support to become prime minister.

Mark Carney: The Banker

Mr. Carney is a former central banker who made his first foray into politics by winning the support of Liberal Party members to replace Justin Trudeau as the party’s leader last month.

In succeeding Mr. Trudeau, Mr. Carney became prime minister, in line with Canada’s parliamentary system. He has distinguished himself as a monetary policy-making and finance executive and is at ease in the high-power circles of the World Economic Forum at Davos.

His supporters mention this background as evidence of his deal-making competence and ability to move around power and money with ease; his critics cite the very same attributes as proof that he’s an out-of-touch elitist.

In the general election, he is running for a parliamentary seat in a middle-class neighborhood in Ottawa.

Mr. Carney was born in Fort Smith, in the Northwest Territories, and grew up playing hockey in Edmonton, Alberta. His parents were teachers. He is married to a British economist, Diana Fox Carney, and has four children. He was educated at Harvard and Oxford.

Framing his lack of experience in politics as an asset, Mr. Carney has presented himself as an outsider with a long record of public service and private-sector chops that make him the best person to stand up to Mr. Trump’s tariffs and annexation threats, and steady the country through economic tumult.

After a 13-year career in Goldman Sachs offices around the world, Mr. Carney moved to Ottawa to serve in the senior ranks of Canada’s finance department, and then as governor of the Bank of Canada from 2008 until 2013. In that role, he helped Canada avoid a financial crisis as the U.S. banking system melted down.

Mr. Carney led the Bank of England from 2013 until 2020, and tried to steady the British economy through Brexit.

He recently served as an adviser to Mr. Trudeau, a fact his detractors cite as evidence he is just Mr. Trudeau by another name.

Mr. Carney tends to speak deliberately and can come across as stiff or professorial. The rare interviews he has agreed to, including one last week with the Canadian cultural icon Nardwuar, have shown a lighter side.

Pierre Poilievre: The Politician

Mr. Poilievre has been involved in Conservative politics for two decades. At 24, he was Canada’s youngest member of Parliament in 2004, eventually becoming a cabinet minister under Stephen Harper, the Conservative prime minister who preceded Mr. Trudeau.

He has earned a reputation as a potent attack-dog politician on the party’s right who doesn’t shy from a fight and uses his sharp rhetoric and a disciplined performance to drill in his point.

As Conservative leader over the past three years, he has made his mark with three-word slogans, harvesting Canadians’ grievances with the stewardship of the country under Mr. Trudeau and the Liberal Party.

Like Mr. Carney, Mr. Poilievre grew up in Alberta and was raised by teachers, who adopted him from his mother, who had given birth to him at 16.

Mr. Poilievre’s wife, Anaida Poilievre, and their two young children have been prominent on the campaign trail, which has focused on crime deterrence, unaffordable living costs and buttressing Canada’s security, with promises to cut taxes and shrink government.

Up until January, Mr. Poilievre was considered a shoo-in to lead the Conservatives to victory in the federal elections and become the next prime minister. But things turned rapidly against him after Mr. Trudeau resigned, allowing Mr. Carney to appear as the shiny new face of the beleaguered Liberal Party.

And then came Mr. Trump’s election and his attacks on Canada’s sovereignty and economy.

Opinion research shows Mr. Poilievre has been harmed by comparisons to the American president. The two share a few pet sets of opinions — dislike for mainstream news media and big government, and support for cryptocurrencies and oil drilling. But what has mostly driven the comparisons has been Mr. Poilievre’s occasional use of harsh, pointed language.

Mr. Poilievre has been credited with “professionalizing” the Conservatives by formalizing the use of political consultants and voter-profiling methods, along with helping the party reach all-time fund-raising highs.

Who votes and what’s on the ballot?

All Canadian citizens, including prisoners and people who live outside the country, are eligible to vote with one exception. The chief electoral officer, the nonpartisan official assigned by Parliament to run the electoral system, cannot cast a ballot during his or her 10-year tenure.

By tradition, the governor general, who holds King Charles’ powers and responsibilities as Canada’s head of state, abstains from voting to protect the office's political neutrality.

Voters have a single task: to select their local member in the House of Commons, the elected assembly of Canada’s Parliament. The next Parliament will have 343 members, an increase of five since the last election because of population growth.

Canada uses a “first past the post” system, in which the candidate with the most votes wins the seat, even if that total is not a majority of the ballots cast.

There is no voting on referendums or for other offices.

What are the issues?

President Trump’s tariffs on Canadian exports and his repeated calls to make the country as the 51st state have dominated the campaign.

Many Canadians view the vote as a referendum on who can best handle Mr. Trump, while also coming up with a plan to lessen the harm to the country from the economic turmoil the tariffs has created.

Polls show that many Canadians consider Mr. Carney better suited to take on Mr. Trump and that has helped the Liberal Party erase a double-digit lead by Conservatives.

Inflation, particularly the high cost of groceries and soaring house prices, were issues that Mr. Poilievre used to rise to what once looked like a certain election victory before Mr. Trump started taking aim at Canada and helped boost Liberals to the lead in surveys.

Both the Liberals and Conservatives are promising tax cuts and with the country’s sovereignty under threat, the two parties have also pledged to increase military spending.

Climate change, a major topic in previous elections, has received relatively little attention, as have issues related to Indigenous people, another important area for Mr. Trudeau.

How do I vote?

Most Canadians have received a card in the mail indicating their polling place and locations for four days of advanced voting, which began on April 18. Elections Canada, a nonpartisan agency that administers Canada’s election, has an online service for people whose cards have errors or who have not received a card.

While having a card makes voting easier, it is not required.

(About 7.3 million Canadians cast their ballots during the advanced voting period, which took place from April 18 to April 21, according to Elections Canada, a 25 percent increase over advanced voting in the 2021 election.)

People who live outside of Canada or who won’t be in their communities either on Election Day or any of the advance voting days have until April 22 to apply for a mail-in ballot, which can also be handed in at any election office.

Any ballots that reach Elections Canada in Ottawa after 6 p.m. Eastern time on voting day will not be counted.

Who are the leaders?

Mr. Carney, 60, the Liberal Party leader who has been serving as prime minister since early March, is a political novice. He has had a long career in central banking and global finance.

Mr. Poilievre, 45, the Conservative Party leader, has been a politician for most of his adult life and is well known to voters, having meticulously curated his agenda, talking points and image.

Two other candidates are vying to maintain their parties’ representation in Parliament: Jagmeet Singh of the New Democrats, a leftist party that has focused much of its campaign on health care and that has seen its support in polls sink to the lowest level since 2000, and Yves-François Blanchet of the Bloc Québécois, which runs candidates only in Quebec. The Green Party is also running candidates in many districts across the nation.

But Mr. Poilievre and Mr. Carney are widely acknowledged to be the only two who can gain enough support to become prime minister.

Who elects the prime minister?

No one directly. In general, the party that emerges with at least a plurality of seats in the House of Commons will ask the governor general to allow it to form the government. The leader of the party that forms the government becomes prime minister, and he or she then chooses a cabinet, usually from the party’s members in the House of Commons.

The prime minister is not required to be a member of Parliament. Mr. Carney, succeeded Justin Trudeau last month after Liberal Party members elected him as their leader. He is now running in his first election, to represent a middle-class suburb of Ottawa rather than the affluent neighborhood where he, along with many diplomats, lives.

One issue dominates

President Trump’s tariff attack on Canada and his repeated calls for the annexation of the country as the 51st state had consumed Canadians before the vote was called and continued to dominate the campaign. Many Canadians view the vote as a referendum on who can best handle Mr. Trump while devising a plan to mitigate harm to the country from the economic turmoil the president has created.

Inflation, particularly on food, and soaring house prices in much of the public were the issues that Mr. Poilievre used to rise to what once looked like a certain election victory. Both the Liberals and Conservatives are promising tax cuts.

With the country’s sovereignty now threatened but leaders have vowed to increase military spending.

Climate change, a major topic in the three previous elections, has received relatively little attention as have issues related to Indigenous people, another important area for Mr. Trudeau.

When are the results known?

Canada has six time zones, but poll closing times are staggered so that most of them shut at 9:30 p.m. Eastern time regardless of where they are. The Westernmost province British Columbia closes half an hour later, at 10 p.m. Eastern time. The results of the election will, most likely, be known on the evening of April 28.

Canada uses paper ballots that are counted by hand at every polling station, by employees of Elections Canada. Candidates are allowed to appoint representatives to oversee the counting. No counting machines are used.

The polling station results are then reported upward to Elections Canada’s headquarters in Ottawa, which releases them online, immediately.

Because the ballot boxes are not moved to central counting locations, the first results usually begin trickling in soon after the polls close. The full count usually extends until well after the broad result of the election has become clear.

Special ballots used for people voting by mail, prisoners, Canadians outside of the country and military members are generally not counted until after voting day to allow officials to confirm they did not vote in person.

What if no party gets a majority of seats?

Canada does not have a history of European-style coalition governments, in which several political parties join together to form a cabinet and govern. The one exception was during World War I, when the Conservatives and some of the Liberals in the House of Commons, along with independent members, formed a coalition to deal with growing political divisions over conscription.

Minority governments formed by the party that wins the most seats, however, are common. They usually rely on the informal support of other parties to pass legislation. But such governments live in constant peril of being brought down by losing a confidence vote in the House of Commons or being defeated on a bill that involves taxes or spending money.

In 1979, a Progressive Conservative government only lasted 66 days before being defeated, forcing another election.

The New Democrats formally agreed to support Mr. Trudeau after the 2021 election, in exchange for the Liberal Party adopting some of its policy measures. But the New Democrats were never part of Mr. Trudeau’s government.

Matina Stevis-Gridneff contributed reporting.