Until January, polls suggested that the Conservative Party would handily regain power from the Liberals in any Canadian election held this year.

Two things overturned that expectation: the resignation of Justin Trudeau as prime minister and President Trump’s trade war with Canada, along with his threat to annex the country and make it the 51st state by sowing economic chaos.

While Mr. Trump pulled back from his initial threat of tariffs on everything imported from Canada, he has imposed several measures that hit key sectors of Canada’s economy: a 25 percent tariff on automobiles, aluminum and steel, and a similar one on Canadian exports that do not qualify as North American goods under the United States-Mexico-Canada Agreement, which he signed during his first term in office. An auto parts tariff of 25 percent is scheduled to take effect on Saturday.

Last week, Mr. Trump suggested that the automobile tariffs, which are reduced based on their U.S.-made content, could be increased. He offered no specifics.

Autos and auto parts are Canada’s largest exports to the United States, outside oil and gas.

Under Mr. Trudeau, Canada placed retaliatory tariffs on U.S. goods coming into Canada that are expected to generate 30 billion Canadian dollars, about $22 billion, in revenue over a year.

After becoming prime minister in March, Mark Carney imposed an additional 8 billion Canadian dollars, about $5.7 billion, in tariffs, including a 25 percent levy on autos made in the United States — but not on auto parts. Automakers with assembly lines in Canada will still largely be able to bring in American-made cars of those brands duty free.

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