Representative Sheila Cherfilus-McCormick, the Florida Democrat charged with embezzling $5 million in federal disaster aid and using it for her campaign, announced her resignation from Congress on Tuesday, just minutes before the House Ethics Committee had been set to vote on whether to recommend that the House expel her.

Ms. Cherfilus-McCormick, 47, was indicted in November on charges of stealing Federal Emergency Management Agency money and funneling some of it to her 2021 congressional campaign. The ethics panel had been investigating the matter for more than two years, reviewing tens of thousands of documents related to accusations that the Republican chairman, Representative Michael Guest of Mississippi, described on Tuesday as “extremely serious and extremely complicated.”

The committee, which last month found Ms. Cherfilus-McCormick guilty of 25 violations including campaign finance infractions and false financial disclosures, had been preparing to vote on whether to recommend a sentence of expulsion to the full House. Such a penalty, which requires a two-thirds majority vote to oust a colleague, is an extremely rare occurrence that has happened only six times in the history of the chamber.

Instead, Ms. Cherfilus-McCormick pre-empted the action, issuing a fiery statement that said she was resigning, about 20 minutes before the panel had been set to meet. When the committee convened, her brief official resignation letter was read into the record and the session was abruptly adjourned because the committee no longer had jurisdiction.

“I will not stand by and pretend that this has been anything other than a witch hunt,” she wrote in a separate statement she posted online.

Ms. Cherfilus-McCormick, whose case is expected to go to trial next year, has denied wrongdoing. If convicted, she could face up to 53 years in prison.

The two-thirds supermajority needed to expel a member of Congress is a purposefully high bar for overruling the will of the voters. But the vast majority of her colleagues in both parties had been expected to vote to remove Ms. Cherfilus-McCormick, and many of them said they were not surprised by her decision to resign instead.

She was the third lawmaker in less than two weeks to resign from Congress under the threat of potential expulsion. Representative Eric Swalwell, Democrat of California, announced last week that he would quit amid allegations that he sexually assaulted a former staff member and engaged in misconduct with other women. The decision came after Representative Anna Paulina Luna, Republican of Florida, had filed a motion to expel him.

Representative Tony Gonzales, a Texas Republican accused of having a coercive sexual relationship with a staff member who later killed herself, also said last week that he would step down. Representative Teresa Leger Fernández, Democrat of New Mexico, had been planning to file a motion to expel Mr. Gonzales if he did not resign.

Another lawmaker who could face potential expulsion is Representative Cory Mills, Republican of Florida, who was investigated by the Metropolitan Police Department in Washington, D.C. last year in connection with a report of an assault on a woman. His former girlfriend was issued a protective order against him after accusing him of threatening her with revenge porn after she broke up with him. He has also been under investigation by the ethics panel and has vehemently denied wrongdoing.

Representative Nancy Mace, Republican of South Carolina, on Monday introduced a motion to expel him. Mr. Mills told reporters on Tuesday that he had no plans to resign and complained that lawmakers were getting ahead of the ethics committee’s notoriously long and laborious process for investigating members. He said he did not believe that Ms. Mace had the votes to force his expulsion. She has not yet called up the resolution.

The serious allegations against all four lawmakers have become a major distraction on Capitol Hill in recent days. Months before the midterm elections, they have also served as a reminder of the kind of behavior by public officials that sours voters on both parties at a time when the country is embroiled in a military conflict with Iran and a partial government shutdown.

Ms. Cherfilus-McCormick, who has been serving in Congress since winning a special election in 2022, was the only one of the four lawmakers who was not facing allegations that were sexual or violent in nature. She had been under investigation the longest.

Representative Mark DeSaulnier of California, the ranking Democrat on the Ethics Committee, said at last month’s rare public trial that the allegations “implicate the public’s confidence in the House’s integrity as an institution.”

Ms. Cherfilus-McCormick’s resignation means she will give up her $174,000 congressional salary at a time when she still has mounting legal bills. Her federal trial was recently postponed until February 2027.

In the statement she posted online, she was defiant, warning of the precedent of punishing people “before due process is complete,” and saying that “we do not allow allegations alone to override the will of the people.”