Results are starting to come in. Here’s the latest.

Officials in Canada are tallying votes in the country’s deeply consequential election, and a new prime minister could be decided within hours. Polls have closed across most of the country, where voters are determining how it will respond to President Trump’s threats and the shape of its economy at a time of global turmoil.

Pre-election opinion surveys showed the Liberal Party, led by Prime Minister Mark Carney, with a slight advantage over the Conservative Party and its leader, Pierre Poilievre, as voters headed to the polls to elect their parliamentary representatives. The leader of the party that wins the most seats will become prime minister.

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 appeared 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 are 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 last month. 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 put off some voters, who see him as too similar to Mr. Trump at a time when the U.S. president is seen as an enemy of Canada.

• 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.