Washington(CNN) Democrat Sara Gideon has conceded the Maine Senate race to Republican Sen. Susan Collins in one of the most competitive and closely watched races in the fight for control of the Senate, potentially denying Democrats a top takeover opportunity and significantly narrowing their path to the majority.
"Just now, I spoke with Senator Collins. I congratulated her on winning this election," Gideon, the state House speaker, said in a concession speech Wednesday afternoon.
"While we came up short, I do believe that Mainers in every corner of this state are ready to continue to work together to make a difference," she said.
CNN has not projected the winner of the Senate race.
The defeat would be a major blow to Democrats, who have already come up short over the past 24 hours in a number of races where they were competing in hopes of flipping the chamber. Democrats' chances of controlling the Senate are now rapidly diminishing.
Both parties have so far flipped a seat each with Republican Tommy Tuberville, the former Auburn football coach, unseating Alabama Democratic Sen. Doug Jones and former Gov. John Hickenlooper defeating Republican Sen. Cory Gardner in Colorado.
Senate Democrats had made Maine one of their top targets, in part because Hillary Clinton carried the state in the 2016 presidential election. Along with Gardner, Collins was one of just two Republicans running for reelection in a state Clinton won. This year, Democratic nominee Joe Biden has won at least three of the state's four electoral votes, CNN projects.
Despite the state as a whole going for the Democrat at the top of the ticket, Collins -- a long-time incumbent who has served in the Senate since 1997 -- was confident she had held on.
Collins' office confirmed the Democratic challenger had called her to concede, and the senator announced she had won reelection in Maine at a Wednesday news conference in Bangor.
"I want to publicly thank Sara for her call, we had a good time, and I very much appreciated her taking the time to call," Collins said.
"Let me say what an extraordinary honor it is to represent the great state of Maine and to know that I will have the opportunity to serve all of Maine for the next six years," she added.
Republicans had been worried that even if Collins came out on top, if she didn't surpass 50% of the vote, she might lose in ranked choice voting, which allows voters to rank candidates in order of preference on the ballot, if they choose to do so.
Collins has worked to cultivate a moderate and independent brand while serving in the Senate.
In July, she declined to back President Donald Trump for reelection, saying instead she would focus on her own race while suggesting that she only picked sides in 2016 because she was not on the ballot.
Scott Reed, a veteran GOP strategist who led the pro-Collins super PAC 1820 PAC, told CNN that Collins' decision to decline to say whom she would support for president "reinforced Susan's independence, that she's above party politics, that she's for Maine."
Reed said Collins' decision to oppose the nomination of Supreme Court Justice Amy Coney Barrett was also in line with the vast majority of Maine voters. "They didn't agree that the seat should be filled before the election," he said.
Political groups spent over $135 million on ads in the Maine Senate race, according to Kantar/CMAG, 57% of which was from Democrats.
"The amount of national resources that went into Gideon's campaign proved to be Schumer's follies," Reed said, referring to the Senate minority leaders.
This story has been updated with additional details Wednesday.