In an escalation of the GOP’s efforts to distance the rest of the conference from Congressman Matt Gaetz, Senator Mullin is reviving a scandal that has dogged the Florida congressman since 2021.

On CNN, Mr. Mullin dredged up the details of an ethics investigation and a Department of Justice investigation into Mr. Gaetz relating to allegations that he had trafficked a 17-year-old girl for sex.

Mr. Mullin said that when the news broke that this investigation was ongoing in 2021, “The media didn’t give [Mr. Gaetz] the time of day” because he was seen as a fringe figure in the party. He explained why, in his opinion, none of his colleagues defended Mr. Gaetz, saying it was “because we had all seen the videos he was showing on the House floor — that all of us had walked away — of the girls that he had slept with,” Mr. Mullin said. “He would brag about how he would crush E.D. medicine and chase it with energy drinks so he could go all night.”

Mr. Gaetz, responding to CNN, said, “This is a lie from someone who doesn’t know me and who is coping with the death of the political career of his friend Kevin. Thoughts and prayers.”

“I don’t think Markwayne Mullin and I have said 20 words to each other on the House floor,” Mr. Gaetz said.

The justice department’s investigation into Mr. Gaetz ended in February, yet he is still facing a probe by the House Committee on Ethics into the allegations, one that some have speculated could have contributed to his antagonism toward the former speaker, Congressman Kevin McCarthy.

Mr. Gaetz has denied that the House investigation into the allegations played any part in his desire to oust Mr. McCarthy, telling Fox News that the theory is “an urban legend.” Mr. McCarthy, as recently as Monday, insisted that he couldn’t block the investigation.

Mr. Mullin’s comments are part of a larger turn against Mr. Gaetz within the GOP and represent an escalation of a fight that is poised to get even more personal ahead of the speaker election next week.

On the House floor during the proceedings leading to Mr. McCarthy’s ouster, Congressman Garret Graves was among those who were most critical of Mr. Gaetz, accusing him of fundraising off the effort to remove Mr. McCarthy.

“All of a sudden, my phone keeps sending text messages. Text messages saying ‘Hey, give me money,’” Mr. Graves said. “Oh, look at that. Oh look, ‘Give me money. I filed the motion to vacate.’ Using official actions, official actions to raise money. It’s disgusting. It’s what’s disgusting about Washington.”

Since Mr. McCarthy’s removal, some representatives, like Congressman Don Bacon, have said that they would support removing Mr. Gaetz from the conference, though it’s not clear whether such an effort would succeed. 

Some, such as Congresswoman Marjorie Taylor Greene, have said that such an effort would incur backlash from GOP voters. “A Republican-led effort to expel Matt Gaetz absolutely will not be tolerated by Republicans across the country,” Ms. Greene said in a tweet.