Representative Nancy Mace, the South Carolina Republican who in recent weeks has floated a run for governor, on Monday night accused her former fiancé and three other men of having drugged and raped her and other women, and of filming and taking lewd photographs of women and underage girls without their consent.

In a stunningly graphic speech on the House floor that had little precedent, Ms. Mace said the men, whom she named and displayed photographs of on a placard where lawmakers more typically display charts and graphs on policy issues, were involved in the “premeditated, calculated exploitation of innocent women and girls in my district.”

“You’ve booked yourself a one-way ticket to hell,” she said, referring to the men directly at one point in a speech that lasted close to an hour. “It is nonstop. There are no connections. So I and all of your victims can watch you rot into eternity.”

On the floor of the House, Ms. Mace was protected by the speech and debate clause, even as she accused the men of repeatedly assaulting incapacitated women and filming it. She offered no evidence to support the accusations, although she said she had plenty of such material.

She refused to answer any follow-up questions from reporters outside the Capitol on Monday night and did not respond to a separate request to provide corroboration. The New York Times has not independently verified any of the allegations.

In a statement not long after Ms. Mace finished speaking, Patrick Bryant, the former fiancé whom she accused by name, denied her account.

“I categorically deny these allegations.,” he said. “I take this matter seriously and will cooperate fully with any necessary legal processes to clear my name.”

Ms. Mace has long made her personal trauma part of her political brand. In the past, she has shared the story of being molested at a swimming pool when she was 14 and said that for years she blamed herself, because she had been wearing a two-piece bathing suit. She said she was raped when she was 16, leading her to drop out of high school, before pulling herself out of a downward spiral and becoming the first woman to graduate from the military college the Citadel.

Ms. Mace has tried to position herself as the ultimate defender of women’s rights, even as she has expressed unequivocal support for President Trump, who has been found liable for sexual abuse, and a cabinet member who has been dogged by an accusation of sexual assault that he has denied. In recent weeks, Ms. Mace has made a campaign out of her measure to bar transgender individuals from using women’s restrooms and changing rooms in the Capitol complex.

A onetime moderate who has made a full-bore turn to Trumpism as she has tried to game out her own political future in a tribal party, Ms. Mace has been vocal in recent weeks about her interest in running for governor in her state.

So has Alan Wilson, the South Carolina attorney general, whom she targeted in her speech on Monday as a “do-nothing attorney general” and accused of treating women who came forward like criminals.

“During the last year, as I turned everything over to law enforcement, I was told I, as a victim, would be investigated,” she said.

A spokeswoman for Mr. Wilson, Jaqueline Lane, said that Ms. Mace’s statements regarding the conduct of the attorney general were “categorically false.”

“At this time, our office has not received any reports or requests for assistance from any law enforcement or prosecution agencies regarding these matters,” said Ms. Lane, who added that neither Mr. Wilson nor anyone in his office had heard of Ms. Mace’s allegations until she spoke out on Monday night.

She said that while Ms. Mace and Mr. Wilson had been at multiple events together over the last six months and the congresswoman had the attorney general’s cellphone number, “not once has she approached or reached out to him regarding any of her concerns.”

On the House floor, Ms. Mace said that on her last night with her former fiancé, he “physically assaulted me,” leaving a permanent mark on her body. Before that, she said, she had found about a dozen compromising photos of underage girls on his phone, as well as more than 10,000 videos documenting assaults of other women who appeared to be incapacitated at the time, and graphic images of women that appeared to have been recorded surreptitiously.

She was shocked, she said, to zoom in on one of the videos and discover that she was one of the women who had been filmed nude, without her consent.

Ms. Mace gave her speech in a mostly empty chamber after House votes. But three female Republican lawmakers, Lauren Boebert of Colorado, Anna Paulina Luna of Florida and Victoria Spartz of Indiana, sat behind her in solidarity.