The Democratic nominee for Senate in Maine, Graham Platner, said Monday that he is “taking the time to reflect” on his bid for US Senate after a former girlfriend accused him of sexual assault.

It is the latest — and most serious — allegation to roil his challenge against Republican Senator Susan Collins. Platner denied the allegations, which were first reported by Politico, in a video statement on social media, but added that “regardless of the inaccuracy of the reporting, but mindful the political reality it will inflict, we are taking the time to reflect on the best path forward.”

Several Democrats have called on Platner to withdraw his nomination in the hours since Politico’s report. Platner has also faced controversy over a now-covered Nazi tattoo on his chest, sexually explicit text messages he sent to women while married, and accusations that he showed “unsettling” behavior towards past girlfriends, per a report from the New York Times.

Democrats could replace Platner if he redraws from the race by Monday. Maine’s Senate race is considered key for Democrats’ chances of reclaiming the upper chamber this midterm.

Here’s a rundown of who has asked Platner to bow out — and which key Democrats have remained silent.

Elizabeth Warren and Ed Markey

The Massachusetts senators were some of Platner’s most influential Democratic endorsements. Warren attended a rally in Portland for Platner in April, calling him a “real fighter” for Mainers. Markey endorsed Platner in June after he won the Democratic primary.

On Monday, Warren said in a statement that there “can be no tolerance for sexual assault” and urged Platner to step down.

“With so much at stake, the best path forward is for Graham Platner to step aside as the Democratic nominee and address these serious allegations outside this Senate race,” she said.

Markey posted on X on Monday: “The allegations reported against Graham Platner are deeply disturbing and must be taken seriously. I cannot support his candidacy.”

Bernie Sanders

Vermont Senator Bernie Sanders said in a statement Tuesday that he spoke with Platner and “recommended that he step aside” amid the “very serious allegations.”

Sanders appeared at multiple rallies for Platner in Maine and doubled-down on his endorsement last month after reports surfaced that Platner sent explicit messages to several women while married.

Senator John Fetterman of Pennsylvania, who has repeatedly criticized Platner, told Fox News on Monday that he thinks Sanders should “apologize for pushing this kind of predator more than anyone.”

Maine Democratic Party

The Democratic Party of Platner’s home state called on him to withdraw shortly after Politico’s report on Monday.

In a statement, Maine Democratic leaders said the party “stands with women and survivors, and that principle does not bend based on party affiliation.”

“We are entrusted with deciding who represents our value and who carriers our banner” read the statement. “That responsibility requires judgement, leadership, and a willingness to act when circumstances demand it.”

“This Senate race comes at a pivotal moment in the struggle against a government, supported by Senator Collins, that serves the interests of the wealthy and powerful at the expense of ordinary Maine people,” it continued. “It is essential that we refocus this campaign on that struggle.”

In a separate statement, Maine Democrats addressed the timeline for potentially replacing Platner as the nominee if he does drop out. Party leadership urged that the “sooner this process can begin, the more time we will have to administer an intentional and inclusive process for Mainers and Democrats.”

Chuck Schumer and DSCC

Chuck Schumer, the Senate’s top Democrat, released a joint statement with the Democratic Senatorial Campaign Committee on Monday calling for Platner to drop out.

“Graham Platner needs to immediately withdraw as the Democratic nominee for Senate and allow Maine Democrats the opportunity to choose a new candidate who can defeat Susan Collins,” read the statement from Schumer and DSCC chair Kirsten Gillibrand.

The statement added that the DSCC “will not invest in the Maine Senate race if Platner remains on the ballot.”

Schumer originally backed Maine Governor Janet Mills for the state’s Senate Democratic nominee. Mills suspended her campaign in April after running out of money.

Janet Mills

The Maine governor has not commented on Platner’s candidacy, nor has she endorsed him, since she ended her campaign for Senate.

Prior to the Democratic primary in Maine last month, Mills reminded voters she was “still on the ballot.” According to the Associated Press, Mills won 19.2 percent of the vote on the June 9 primary. Platner, the projected winner, won 72.1 percent.

Zohran Mamdani

New York City Mayor Zohran Mamdani, another prominent progressive voice, was asked about Platner during a press conference Tuesday morning.

“I believe it is time for him to drop out of the race,” Mamdani told reporters.

Later in the press conference, Mamdani was asked if he believes Platner’s campaign could hurt the broader progressive movement.

“I think the focus of today should be on the campaign coming to a close, and I think there will be many more days to have conversations about what it means beyond that,” Mamdani said.

Other national Democrats

California Democratic Representative Ro Khanna, a prominent voice among progressives, posted on X on Monday that he was withdrawing his endorsement for Platner.

“I’ve been very clear that sexual assault or violence against women is a red line,” read the post. “These allegations are very serious and credible. Graham Platner should drop out from the race.”

Arizona Senator Ruben Gallego, a fellow Democrat, also rescinded his endorsement.

“The allegations against Graham Platner are troubling and deeply serious,” Gallego said on X.

Progressive Michigan Representative Rashida Tlaib said on Tuesday that she was “withdrawing my endorsement of Graham Platner and calling on him to exit the race immediately so that he can be replaced by a progressive fighter who will deliver for the people and help win back the Senate.”

“These allegations are devastating and must be taken seriously,” she added on X.

Kaitlin Lewis can be reached at Kaitlin.Lewis@globe.com. Follow her on X @kblewey.