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. Trump’s Trade War 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.