Miller, a senior adviser to Trump during his first presidency, faced a Wednesday deadline to decide whether to stay in his race for reelection, with Republicans nervous that the allegations surrounding the second-term congressman could cost them a seat as they try to hang on to their House majority in this year's midterms.
Leaders of the ethics committee said in their statement that the committee was reviewing whether Miller "may have engaged in domestic violence and abuse or illegal drug use." Earlier in the day, Miller said he had requested his own investigation into the allegations made by his ex-wife, Emily Moreno. It was not clear whether his request or another one prompted the committee to investigate.
Trump spoke with Miller on Monday and advised that his candidacy "doesn't look good," according to a source familiar with the conversation who was granted anonymity to discuss a private conversation. Trump's conversation with Miller was first reported by Axios.
But Miller, in announcing his plans on the social platform X to request an ethics probe, said, "I have nothing to hide" and that he was seeking "to clear my name."
The former Trump aide whom the president endorsed in May is facing a flurry of legal filings by his ex-wife, who is the Republican senator's daughter, and an ex-girlfriend.
Sen. Moreno, who until Sunday had remained quiet about the allegations at his daughter's request, on Tuesday described the impact on his daughter, granddaughter and wider family as "truly the seventh level of hell."
"This has been brutal beyond comprehension," he told reporters at the Capitol. "And if there's any minimum standard for being a public official, as I said, he fails to meet that minimum, basic standard."
Asked about the election implications of the allegations for Republicans, Moreno told reporters, "I don't care about the politics at all."
Moreno expressed concern for his granddaughter and told reporters that he traveled Sunday to a suburban Cleveland police station, where Miller was dropping off their daughter. Miller and his ex-wife share custody of the 2-year-old.
Miller had previewed his intention to stay in the race over the weekend when he livestreamed a video defending himself on X and posting a cache of documents related to his divorce and custody cases.
"I'm not dropping out of this race and I'll win in November," he said on the platform.
Sen. Moreno said the video prompted him to break his silence and call for Miller to no longer hold public office.
Trump declined to say publicly on Monday whether Miller should exit the race, noting that the accusations against him were "allegations."
"I know Max. He's a good person. I mean, I always thought he was a very good person. And I'm going to let the families figure that out," Trump told reporters when asked about Miller during an Oval Office event.