PORTLAND, Maine — A recount that promises to be long and laborious began Thursday in a Maine congressional race that used a new voting system where voters rank candidates.

State election officials started the recount, requested by Republican U.S. Rep. Bruce Poliquin in the 2nd Congressional District. The process of manually recounting the ballots is projected to take four weeks to complete.

That means the announcement of the result will likely come close to the date that Democratic Rep.-elect Jared Golden is to be seated. Golden defeated Poliquin in the historic race, which asked Maine voters to rank four candidates.

"We've never done this kind of a recount. We'll see how it goes," said Kristen Muszynski, a spokeswoman for the Maine Department of the Secretary of State. "We're doing the recount by hand."

Poliquin won the first round of votes and has said he believes he should be declared the winner. But the election swung to Golden after two independents were eliminated and their second-choice votes were reassigned in ranked-choice voting. Poliquin later requested the recount.

"With an election that has had so many high profile issues, it is important for every vote to be counted accurately," said Maine Republican Party executive director Jason Savage.

The recount is the latest turn in a long, sometimes bitter election between the Republican congressman and businessman and the Democratic state representative and Marine veteran. Poliquin has cast doubt on the ranked-choice system, which voters approved in 2016, but Golden has defended it as the will of the people.

"This is just more politics from the Bruce Poliquin campaign," said Golden's campaign manager, Jon Breed. "I do not think the result is going to change."

Poliquin is also asking a federal judge to nullify the results on constitutional grounds. He wants the judge to declare him winner or order a new election. The judge heard arguments in the case on Wednesday and said he intends to make a ruling by next week .