When protesting truckers rolled toward downtown Ottawa and proceeded to occupy the Canadian capital for four weeks, they got a welcome from a man waving to them from a highway overpass, his hands covered in knitted red mittens with white maple leaves on the palms.

The man was Pierre Poilievre, who would become the leader of the Conservative Party and who until just recently was widely referred to as Canada’s next prime minister. Soon he will have a new title: ex-Member of Parliament.

In a stunning upset, voters in Mr. Poilievre’s district (or riding, as it is known in Canada) turned him out of office on Monday. His embrace of the so-called Freedom Convoy of 2022, appears to have played a significant role in the defeat.

Voters in this part of Canada have memories of that time — and not fond ones.

With Ottawa paralyzed, local businesses forced to shut down and residents struggling to sleep amid the round-the-clock air horn blasting, Mr. Poilievre brought coffee and doughnuts to the truckers, who were protesting pandemic restrictions and the Liberal government of Prime Minister Justin Trudeau.

On Tuesday, his support for the convoy, some leaders of which recently received criminal convictions, was a recurring complaint among voters in his district, Carleton.

“Populist politics is not for me,” declared one voter, Rick Pauloski, who said he had supported Conservatives in the past.