Jared Golden, a Marine Corps veteran and Democratic state lawmaker in Maine, defeated New England’s lone House Republican, Bruce Poliquin, on Thursday, just two days after Mr. Poliquin filed a lawsuit to stop the counting of votes under the state’s new ranked-choice voting system.
Mr. Poliquin’s defeat added to a swell of bad news for northeastern Republicans, who suffered heavy losses on Election Day, and gave Democrats another Republican seat in their takeover of the House.
A spokeswoman for the Maine Secretary of State’s office said the results remained unofficial pending certification by Nov. 26. But, if certified, the results would make Mr. Golden the winner of a four-candidate race in which Mr. Poliquin was the leader on Election Day but Mr. Golden ended up winning by less than 3,000 votes under the state’s new election system.
After five drawn-out days of vote counting, Mr. Golden won in the Second District, which covers a majority of the state’s land area, much of it rural and densely forested.
No candidate won a majority of the vote on Election Day, so Mr. Golden’s victory came down to a vote administered under the state’s ranked-choice voting system, implemented in 2016. His victory was the first general election to federal office by a ranked-choice runoff.
That new system became the focus of Mr. Poliquin’s ire on Tuesday, when he filed a lawsuit against Maine’s Secretary of State, Matthew Dunlap, to stop the runoff, asserting that he would have won the election under the old voting system. On Thursday morning, a judge rejected Mr. Poliquin’s request for a temporary restraining order to stop the vote counting process.
Under the new system, if no candidate gets a majority, the winner is selected through a series of elimination rounds that knock off poorly performing candidates and reallocate the votes they won to the second choice candidates listed by their voters.
Representative Bruce Poliquin of Maine during a campaign stop in Old Town last month.CreditRobert F. Bukaty/Associated Press
In his lawsuit, Mr. Poliquin argued that ranked choice voting was an “exotic” and unconstitutional violation of the right to vote. The judge, Lance E. Walker, said that, in twice approving ranked choice voting in ballot measures, the citizens of Maine “have rejected the policy arguments Plaintiffs advance” against it.
The Second District was once a Democratic stronghold that Mr. Poliquin, a former state treasurer, turned red in 2014, with a message that his background in finance would make him a job creator. Democrats had been itching to retake the seat ever since.
Democrats placed their hopes this year in Mr. Golden, 36, who served tours in Iraq and Afghanistan and worked for Senator Susan Collins, a Republican, before serving in the Maine House of Representatives as a Democrat.
But Maine’s political culture is famously independent minded, and ranked-choice voting complicated the strategy efforts of both parties.
Mr. Golden’s campaign focused on kitchen-table issues with a distinctly left-wing approach and enacting stronger labor laws.
New England was long welcoming to the Republican Party’s moderate wing, but Mr. Poliquin’s loss leaves the region with just a handful of high-ranking Republican officials including Gov. Charlie Baker of Massachusetts and Gov. Phil Scott of Vermont, both moderates increasingly out of step with the national party, and Ms. Collins.
Mr. Poliquin’s defeat also adds to the grim toll inflicted upon Republican representatives in the Northeast, where the party suffered widespread losses in New York and New Jersey driven in large part by voter hostility toward President Trump, especially in highly educated urban and suburban areas.
Mr. Golden portrayed Mr. Poliquin, who did not endorse Mr. Trump in 2016, as out of touch with the district in large part because of his votes in favor of the Republican tax cut plan and for the repeal of the Affordable Care Act.
Mr. Poliquin rejected that characterization and depicted himself as a practical problem-solver, but it was not enough. Instead, he became the first incumbent to lose a race for re-election in the Second District since 1916.