Graham Platner, the Democratic nominee for Senate in Maine and a onetime star of the progressive movement, suspended his campaign on Wednesday under intense pressure from all corners of his party after a woman accused him of rape.
His departure upends one of this year’s most important Senate races and creates enormous uncertainty about his party’s outlook in Maine, where Democrats believe that defeating Senator Susan Collins, a Republican, is crucial to their efforts to reclaim a Senate majority.
The Maine Democratic Party will hold a convention to choose a new nominee by July 27, the state-mandated deadline. An array of Maine politicians, including several who ran in primaries for other offices this year and lost, have expressed interest in running.
In a video posted on social media Wednesday night, Mr. Platner said that the allegations against him were false but that he was suspending his campaign.
“We are suspending campaign operations,” Mr. Platner said. “This is incredibly difficult, because I know that some will think it’s an admission of guilt, and it most certainly is not. We’re not doing it because of the allegations, we’re doing it because of the structures that are being taken away from us by those in power. And I also feel an immense amount of responsibility to everyone who has worked so hard to get us to where we are.”
His exit is the culmination of a rapid fall from grace after he sailed to political prominence last year, only for his campaign to be upended by scandal after scandal. He confronted revelations that he had a tattoo that resembled a Nazi symbol, the surfacing of offensive old Reddit posts, and reports that he had sent sexual messages to women outside his marriage and that several women who dated him years ago recalled that he had acted in unsettling ways.
The final blow for Mr. Platner’s bid came on Monday, when a Politico report detailed how Jenny Racicot, 41, a Democrat who had dated him, accused him of raping her in 2021. Mr. Platner called allegations of nonconsensual behavior “categorically false” in a video on social media on Monday.
Asked by CNN if Mr. Platner had raped her, she replied, “By definition, yes, absolutely.”
No prominent Democratic groups or officials stepped up to defend him. Within hours, Democrats who had previously vouched for Mr. Platner dropped their support, including Senator Elizabeth Warren of Massachusetts, Representative Ro Khanna of California and Senator Ruben Gallego of Arizona.
By Monday night, so had the Senate Democratic campaign arm. Senators Chuck Schumer and Kirsten Gillibrand of New York, who lead the group, said it would not invest in the Maine Senate race if Mr. Platner remained on the ballot, effectively choking off any remaining hopes that he could win in November. His last prominent supporter, Senator Bernie Sanders of Vermont, called for him to step down on Tuesday.
But Mr. Platner delayed his exit in hopes of influencing who would replace him, telling his campaign team in a private call that he wanted to see a nominee who shared his progressive economic agenda.
Maine Democratic voters nominated Mr. Platner by a landslide in the June 9 primary. He won 72 percent of the vote, running effectively unopposed after Gov. Janet Mills, a moderate backed by party leaders in Washington, suspended her Senate campaign in late April as she struggled to match Mr. Platner in fund-raising or voter enthusiasm. She remained on the ballot and received nearly 20 percent of the vote.
The leading candidates to replace Mr. Platner could include several Democrats who ran for governor and did not win the primary.
They include Shenna Bellows, the Maine secretary of state, and Troy Jackson, a former president of the Maine Senate, who had both endorsed Mr. Platner. They placed third and fourth in the primary for governor. Nirav Shah, a former director of Maine’s public health agency, finished second in the primary and has said he is evaluating whether to run.
Ms. Mills is seen as less likely to be selected. She has not responded to messages.
Mr. Platner, 41, a retired Marine combat veteran, won the support of the left wing of the Democratic Party with his ordinary, workingman image and his promises to challenge the party establishment.
But he was trailed by scandals nearly from the start of his campaign.
He denied the most serious allegations, insisted that any troubling behavior in his past did not reflect who he was today and urged Mainers not to judge him for “the worst thing I said on the internet on my worst day 14 years ago.”
He spoke openly about his struggles with post-traumatic stress disorder, depression and drinking after his military service, casting his candidacy as a vote for change — not only political change, but also personal re-evaluation.
But Ms. Racicot’s account proved too serious for fellow Democrats to ignore. Her accusation that Mr. Platner raped her in 2021 was first reported by Politico, which cited emails Ms. Racicot had sent to her therapist and an acquaintance about the encounter and interviewed a man she had dated and confided in during the years afterward.
Ms. Racicot had described some of what happened that night to The New York Times this spring, saying that he had arrived at her house drunk after she had asked him not to come over. At the time, she declined to share further details of that encounter on the record, but she said that she had found his behavior “reckless” and “unsettling” and that she had cut off contact with him soon after that episode.
She told Jake Tapper of CNN in an interview on Monday that she had hesitated to speak out against Mr. Platner because she “felt really uncomfortable with the responsibility of and the weight of my story and what that might do,” given that she agrees with his politics.
“I understand why people want someone like him in office, and I felt like me coming forward would essentially potentially take that away,” she said. But once the story came out and she was named in it, she said, “I kind of just made the decision that I’m going to say my piece and get it out there.”
In private, some Republicans had hoped that a damaged Mr. Platner would stay on as the Democratic nominee past a July 13 deadline to drop out. But Republicans were also publicly denouncing him after the latest accusation.
Attention will now shift to the nomination process for a replacement, which was determined by a vote of the Maine Democratic Party’s 113-member executive committee on Wednesday night. Whoever is chosen in the convention will have to overcome an abbreviated timeline to have a chance of ousting Ms. Collins, a well-known lawmaker who has long dashed Democrats’ hopes of defeating her.
“The one thing in a situation like this that you can never get back is time, and the clock is ticking toward that July 27 deadline,” David Farmer, a Democratic consultant in Maine, said in an interview on Wednesday.
Of Mr. Platner’s run, he added, “It is a wasted year in what was always going to be a very difficult race.”
Shane Goldmacher and Reid J. Epstein contributed reporting.
