Rep. Debbie Dingell, D-Mich., acknowledged that Democrats made a mistake by failing to take seriously the sexual misconduct allegations against Maine Senate candidate Graham Platner simply because one of his accusers is conservative.

The admission comes as Platner faces growing calls from fellow Democrats to end his campaign against Sen. Susan Collins, R-Maine, following multiple allegations of sexual misconduct that he has denied.

During an appearance on Fox News' "America's Newsroom," co-host Dana Perino asked Dingell whether Democrats mishandled allegations first raised by a former girlfriend of Platner.

"Do you think the Democrats made a mistake in not believing Lyndsey Fifield, the conservative who brought the concerns to The New York Times in the first place?" Perino asked.

"Yes. I didn't sleep the other night," Dingell responded. "I have written an op-ed that I may get somebody to [publish] about when will we actually believe those who come forward. We have made progress, but we haven't changed."

Fifield has accused Platner of physically abusing her during their relationship, including leaving bruises on her arms, and of removing condoms during intercourse without her consent. Platner has denied any wrongdoing and has denied ever becoming physical with her.

The allegations against Platner expanded after another former girlfriend, Jenny Racicot, accused him in interviews with Politico and other news outlets of sexually assaulting her. Platner has denied those claims as well.

Earlier this week, Fifield criticized The New York Times over its coverage of her allegations, saying the newspaper emphasized her conservative political background instead of her accusations.

Fifield, who has worked on Republican campaigns, also said the news organization declined to corroborate her account despite being offered sources.

Dingell has also publicly broken with members of her own party over Platner's candidacy.

Speaking to CNN this week, the Michigan Democrat said she was "yelled at" by fellow Democrats after declining to support Platner and suggested more allegations could surface.

"Quite frankly, I am told that there are more," Dingell said, adding that she is aware of "other credible reports."