Canada Has a New Prime Minister With a Very Hard First Assignment

Mark Carney, a central banker turned politician, steps into his role at a crucial moment as President Trump sets his sights on Canada’s sovereignty and keeps threatening more tariffs.

Mark Carney, who has never held elected office but has a long résumé in economic policymaking and investing, was sworn in Friday morning as Canada’s 24th prime minister. He will have no time to ease into his role.

Canada is experiencing a period of severe instability as its relationship with its closest ally, the United States, has been plunged into an extraordinary crisis since President Trump was elected and began unleashing attacks on its economy and sovereignty.

Mr. Carney will attempt to negotiate with Mr. Trump, who has unfurled a slew of tariffs and threats on Canada including a desire to take over the country entirely, while simultaneously heading straight into a campaign for a federal election.

He does not hold a seat in Parliament, and his party controls only a minority of the seats in the House of Commons, which means he has little choice but to immediately call for a federal election, likely to take place by May.

Mr. Carney, who turns 60 on Sunday, replaces Justin Trudeau who led Canada for nearly a decade. He was elected as Liberal Party leader on Sunday by some 152,000 members of the party, securing 86 percent of the vote.

In a traditional ceremony that involved pledging allegiance to King Charles III, Mr. Carney was sworn in by Mary Simon, Canada’s governor-general, who represents the king as the official head of state. Ms. Simon is the first Indigenous person to serve in that role.