Here’s what you need to know about the rise and fall of Mr. Trudeau and what could happen next.

Who is Justin Trudeau?

Mr. Trudeau grew up in the spotlight as the son of Pierre Elliott Trudeau, the Canadian prime minister. In 2015, at the age of 43, Trudeau became Mr Canada’s second youngest leader after his Liberal Party won a strong parliamentary majority. Mr. Trudeau was savvy with social media and enjoyed it for a long time political honeymoon after his election. (He also had good hair.)

In 2017, Mr. Trudeau was under pressure to oppose Donald J. Trump, the US president-elect. While Mr. Trump limited immigration, Mr. Trudeau reiterated Canada’s openness to asylum seekers, announcing, “Diversity is our strength.”

During his tenure, Mr. Trudeau prioritized two issues. One was climate change. The second was reconciliation with the indigenous population, about the generational damage of a boarding school system that was rife with abuse. He also made good on his promise to legalize marijuana.

In 2019, the Liberals retained their power headed by Mr. Trudeau, but with a smaller margin, and they failed to secure a majority in parliament. The Liberals needed the support of smaller parties to advance Mr. Trudeau’s legislative agenda.

During the 2020 coronavirus pandemic Trudeau became the first Group of 7 leader to self-isolate, after his wife Sophie Grégoire Trudeau, tested positive for Covid-19. (The couple is now separated.) The next year, when his approval ratings were still relatively high, he called a snap election, saying he wanted a strong mandate for his party to lead Canada out of the pandemic and into economic recovery.

Voters returned him to office in 2021, but the Liberals again failed to win a majority in Parliament. Mr. Trudeau has since faced fierce criticism from the conservative opposition over some of his policies regarding the pandemic and recovery.

Why is his government unpopular?

Economics: Inflation in Canada jumped to 8 percent after the pandemic, though it has since eased below 2 percent. Unemployment is still high, around 6.4 percent. The conservative opposition struck Carbon taxation program Mr. Trudeau.

Housing: Housing costs in many major Canadian cities became unsustainable. An economic analysis this year found that in Toronto, Vancouver and Montreal, prices would have to plummet or incomes would have to rise dramatically to restore affordability.

Immigration: In October, Mr. Trudeau said he had tightening of Canadian immigration policy after the country took in nearly three million people over three years, straining health care and other services. “In the tumultuous times we’ve come out of the pandemic, between addressing labor needs and maintaining population growth, we haven’t been able to strike the right balance,” he said.

Scandals: In 2018, Mr. Trudeau was accused of groping a female journalist in 2000, an allegation he refused. In 2019, the Federal Ethics Commissioner ruled that Mr. Trudeau tried bypass, undermine and discredit his former Minister of Justice and Attorney General, Jody Wilson-Raybould, in connection with the criminal case against SNC-Lavalina multinational engineering and construction company based in Montreal. That same year, pictures emerged of Mr. Trudeau wearing black or brownface as a student in the 1990s and as a teacher at a private prep school in 2001.

Infighting: Mr. Trudeau hold on power slipped in September when the left-leaning New Democratic Party deprived the Liberals of the guaranteed support needed to pass the law. This week Chrystia Freeland, Deputy Prime Minister and Minister of Finance, abruptly resigned, sharp rebuke to Mr. Trudeau.

What will happen if Mr. Trudeau resigns?

If he resigns as the head of the party, he will no longer be prime minister. But it is important that he can step down.

Mr. Trudeau has two options: He can say he will step down when the party has a new leader, weeks or months in the future.

Or he can resign immediately. In that case, the party would appoint a temporary leader, who would then not be able to run for the leadership position according to the rules of the Liberal Party.

The next step would be to go to a federal election under a new Liberal leadership. Canada’s next election must be held by October 2025, but the vote could be called or forced earlier.

The next federal election could be triggered at any time in two ways. Mr. Trudeau has the power to dissolve parliament at any time, which would trigger an election. Or, if the opposition defeated the Liberal government in a vote of confidence or a budget bill, the government would fall and an election would follow.

Who are the main candidates to succeed him?

Conservatives: Pierre Poilievre leads the Conservative Party from 2022, branding himself as the anti-Trudeau, practical and down-to-earth. He supported the blockade of the capital of CanadaOttawa, 2022 led by truck drivers who opposed vaccine mandates and pandemic restrictions. Mr. Poilievre has been aiming for the top job in government since at least 1999, when he was a student wrote an essay who won prize money approx what would he do as prime minister.

Liberals: Following her resignation this week, there was widespread speculation that Chrystia Freeland, former Deputy Prime Minister and Minister of Finance, would launch her own campaign to lead the Liberal Party. Other candidates are Dominic LeBlanc, who became finance minister when Mrs Freeland resigned; Melanie Joly, the first Canadian diplomat from 2021; and Mark Carney, former governor of the Bank of Canada, who also led the Bank of England.

Matina Stevis-Gridneff contributed reporting.