PORTLAND, Maine (AP) The last New England Republican in the U.S. House is refusing to concede his election defeat last week, and his legal battle over the constitutionality of Maine's new way of voting is expected to drag on for weeks.

U.S. Rep. Bruce Poliquin led in first-choice votes on Election Day but Democrat Jared Golden was declared the victor after extra tabulations under Maine's ranked-choice voting, used for the first time in congressional races.

Poliquin, the first incumbent to lose the 2nd Congressional District seat in more than 100 years, has promised to keep fighting.

U.S. District Judge Lance Walker, who declined Poliquin's request to stop the tabulations last week, agreed to hear more arguments next month in Poliquin's lawsuit that claims the voting system is unconstitutional.

Poliquin has several options. He could let the process play out in U.S. District Court, seek to bypass First Circuit altogether to go directly to the U.S. Supreme Court, or ask the U.S. House of Representatives to seat him instead of Golden.

His legal options face long odds, legal experts say, and the Democratic-controlled House is unlikely to seat Poliquin over Golden.

Over a week after Election Day, Maine isn't the only state facing legal challenges. In Utah, an incumbent GOP House member sued to halt vote counting.

In Maine, the new voting system, approved in 2016, lets voters rank all candidates from first to last on the ballot. If no one gets a majority, then last-place candidates are eliminated and their second-place votes are reallocated to the remaining field in extra rounds of vote-counting.

Poliquin and Golden each collected 46 percent of first-place votes on Election Day, with Poliquin maintaining a slim edge of about 2,000 votes.

But Golden ended up winning with a lead of nearly 3,000 votes after a computer algorithm reallocated second-place votes from Mainers who preferred two trailing independent candidates.

Maine's top state court last year warned that ranked voting conflicts with the state's constitution, which says the winners of state-level races are whoever gets the most votes, or a "plurality." And so Maine uses ranked-choice only in federal elections and state primary races but not for general elections for governor or the state legislature.

Poliquin argues the U.S. Constitution has always been interpreted to mean whoever gets the most votes wins a House race. But the judge said the Constitution also allows states to specify the "times, places and manner" of federal elections.

Poliquin's lawsuit remains alive despite the judge's Thursday order rejecting his last-ditch effort to halt vote tabulations.

University of Maine School of Law professor Jim Burke warned that Poliquin's refusal to concede sows distrust in the voting system.

"It's causing harm to body politics because people are going to believe he may be saying something valid," Burke said.

Kyle Bailey, who continues to lead Maine's ranked-choice voting campaign, said the judge's comments could breathe new life into unsuccessful efforts to change the Maine Constitution to allow ranked voting for gubernatorial and legislative races. "This puts pressure" on Maine lawmakers, Bailey said.

It could also inspire other states to try ranked-choice voting, Bailey said.

That all depends on how the results are interpreted at a time of constant headlines over the legitimacy of elections, said Corey Cook, who's researched ranked-choice voting in San Francisco and serves as dean of the School of Public Service at Boise State University.

"If ranked-choice voting becomes the way you elect Democrats, it's not going to be adopted around the country," he said.