Just as polls were opening in Canada, Donald Trump said on social media that Canadians should “vote for the man” who would make their country part of the U.S.

Conservatives once had a 25-point lead ahead of Canada's next election. That lead has since vanished. Experts say Trump's actions may changed the course of the election.

Whatever the case, one thing was clear: Mr. Trump is not giving up on his obsession with Canada, and the new government that emerges from Monday’s vote will need to deal with a leader intent on both hurting Canada’s economy with tariffs, and coveting its vast resources.