Just days after winning a stunning election on an anti-Trump platform, Prime Minister Mark Carney of Canada on Tuesday will meet with President Trump, who has imposed tariffs on Canada, America’s closest ally, next-door neighbor and top trading partner, and repeatedly threatened its sovereignty.

With the relationship between the two countries in tatters, the two leaders will sit down in the White House for their first face-to-face discussion, a high stakes encounter that could easily go sideways.

Mr. Trump has claimed that Canada doesn’t deserve to be independent because of its reliance on U.S. trade and defense and has spoken about making it part of the United States.

Mr. Carney was a political novice who was swept to power because Canadians saw him as a steady hand to negotiate with Mr. Trump and guide Canada through economic turmoil because of his background as a policymaker and private-sector executive.

Mr. Carney served a governor of the Bank of Canada during the 2008 global financial crisis and of the Bank of England during Brexit, establishing himself as one of the world’s most prominent central bankers.

He faces an unenviable balancing act.

Canadians who took a chance on him will expect him to push back on Mr. Trump’s belittling and threatening rhetoric against Canada, as he promised he would.