Pierre Poilievre, the leader of the Conservative Party, was unseated as the parliamentary representative of his Ottawa district in a stunning upset that could lead to a fight over his continued leadership of the party.

Mr. Poilievre was first elected in 2004 as the member of Parliament representing Carleton, a largely rural district bordering parts of the Ottawa River. His long-held Conservative seat was flipped to the Liberal Party.

Bruce Fanjoy, the Liberal candidate and a well-known community volunteer who was initially considered a long shot, won the race.

Mr. Poilievre embraced some of President Trump’s positions, railing against “radical woke ideology” while pledging to defund Canada’s national broadcaster and cut foreign aid.

While Mr. Poilievre championed Canada’s large oil and gas industry, Mr. Fanjoy campaigned on “growing the green economy” and “real climate action.”

In a recent opinion essay in the Ottawa Citizen, he wrote, “We need to do more to fight climate change.”

Mr. Fanjoy incorporated common measures to reduce household emissions of greenhouse gases in his own family home in the Ottawa suburbs, according to an article about it in The National Observer. The house was fitted with rooftop solar panels and an electric heat pump, so when the panels generate excess electricity in the summer, he can sell it back to the grid.

“One of the challenges that we face in moving towards a more sustainable world is I think a lot of people think that we’re going to lose benefits, it’s not going to be as nice, we’re gonna have to live in an austere environment,” Mr. Fanjoy told the publication. “I don’t think that’s the case at all. We just do things differently, but it’s going to be better.”