Live Updates: Canada Votes on New Leader in Tumultuous Moment

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.