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.