A Florida politician who is central to the investigation into Rep. Matt Gaetz for possible sex trafficking of a minor signaled Thursday that he will plead guilty in his own federal case, a court entry shows, a troubling development for the congressman as it suggests prosecutors have secured a potentially important witness against him.

Joel Greenberg, a former tax collector for Seminole County, Fla., had since last year been outlining to prosecutors how he and Gaetz (R-Fla.) would pay women for sex using cash or gifts as he tried to negotiate a plea deal to resolve his own legal woes, according to a person familiar with the matter. Gaetz has adamantly denied paying for sex.

On Thursday, a federal court in Orlando scheduled a “change of plea hearing” in Greenberg’s case for Monday, indicating he has reached such a deal.

Rep. Matt Gaetz (R-Fla.) first got involved in politics a decade ago. It didn't take him long to find stardom in the Republican Party. (Drea Cornejo/The Washington Post)

The specifics of Greenberg’s plea were not immediately filed in court, and it was not immediately clear to what specific charges and facts he would admit, or what benefit he would receive for doing so. Plea deals do not necessarily require defendants to cooperate — though doing so is one of the best ways they have to reduce their ultimate sentence, and Greenberg already had been providing investigators with information about Gaetz in hopes of leniency. The deal still must be accepted by a federal judge.

A spokesman for the U.S. Attorney’s Office for the Middle District of Florida, which has been handling the Greenberg case, declined to comment beyond the court entry, as did Greenberg’s attorney. Harlan Hill, a spokesman for Gaetz, noted in a statement that the initial charges against Greenberg stemmed from his fabricating accusations and evidence against a political opponent.

“The first indictment of Joel Greenberg alleges that he falsely accused another man of sex with a minor for his own gain. That man was apparently innocent. So is Congressman Gaetz,” Hill said.

Gaetz, who represents a mostly conservative district in Florida’s panhandle, is known as a strident defender of former president Donald Trump and for his frequent appearances on cable TV news. After a court hearing last month when prosecutors and defense attorneys first revealed they were negotiating, Fritz Scheller, Greenberg’s defense attorney, hinted the development should come as worrisome news for the congressman.

“I’m sure Matt Gaetz is not feeling very comfortable today,” Scheller said at the time.

Greenberg was initially charged last summer in a bare-bones indictment that prosecutors have since superseded multiple times. He now faces a 33-count indictment that includes charges of sex trafficking of a minor, stealing from the tax office he once led and other allegations.

It was in the course of investigating Greenberg, people familiar with the matter have said, that investigators came across evidence linking Gaetz to possible sex trafficking involving a 17-year-old girl. Like others, they spoke on the condition of anonymity to discuss an ongoing investigation.

The Justice Department has since been exploring whether Greenberg procured women for Gaetz and whether the two men sometimes shared sexual partners, including the 17-year-old girl at issue in Greenberg’s case. Gaetz has maintained that he never had intercourse with a 17-year-old, which is considered statutory rape in Florida.

The two men were known to be friends. As far back as June 2017, just months after Greenberg had taken office, Gaetz proclaimed publicly that the tax collector was a “disrupter” who should run for Congress himself. A month later, Greenberg posted a photo of himself, Gaetz and former Trump adviser Roger Stone.

Gaetz repeatedly boasted to people involved in Florida politics about women he met through Greenberg, according to two people who heard his comments directly. These people said Gaetz also showed them videos on his phone of naked or topless women on multiple occasions, including while at parties with Greenberg.

Although Greenberg could be an important witness, helping explain various financial transactions that investigators suspect to be payments for sex, he would also face significant questions about his credibility if he were to ever have to testify against Gaetz.

Greenberg was initially charged with fabricating evidence and allegations that a schoolteacher who was running against him to be tax collector had an inappropriate sexual relationship with a student, and the current indictment against him includes charges of wire fraud and submitting false claims to get an Economic Injury Disaster Loan. Gaetz and his attorneys are likely to seek to cast Greenberg as a liar who made up allegations against the congressman to reduce his own, significant legal exposure, and prosecutors would not be likely to rely on his testimony unless it was corroborated by other evidence.