Rivera’s closest ally, U.S. Sen. Marco Rubio, has been keeping his distance from Rivera as well. The two remain friends and own a Tallahassee home together that briefly went into foreclosure in 2010 when both former state representatives ran for higher office.

Rivera no longer attends high-profile events with the senator or with presidential candidate Mitt Romney, who held an event in Rivera’s district where the congressman was the only top Republican no-show.

Rivera was also absent Monday from the Versailles restaurant for a campaign rally for fellow Republican Congressman Connie Mack, who’s running for the U.S. Senate against Democratic incumbent Bill Nelson.

The Versailles event was headlined by Rubio and Congresswoman Ileana Ros-Lehtinen.

Rubio had previously expressed discomfort with a separate year-old federal investigation into Rivera that stemmed from a secret $500,000 payment from a dog track.

Rivera denied wrongdoing in that case and in this latest incident, involving an unknown political newcomer named Justin Lamar Sternad, who ran against Garcia in the Aug. 14 Democratic primary race.

During the race, Sternad repeatedly went after Garcia, sending out a mailer that repeated a line of attack from Rivera over Garcia’s divorce.

Sternad sent out at least a dozen different types of mailers to tens of thousands of voters.

The costs of printing the mailers, targeting the recipients and sending out the mailers were never originally reported by Sternad — a potential violation of campaign-finance laws that require congressional candidates to list their contributions and expenditures.

Two campaign vendors — John Borrero of Rapid Mail & Computer Services and Hugh Cochran of Campaign Data — said Rivera ran the Sternad operation. Borrero said Rivera helped direct a $7,800 cash payment for one mailer, and the congressman’s close friend Ana Sol Alliegro — who managed the Sternad campaign — delivered envelopes stuffed with cash.

Borrero and Cochran have given statements and turned over evidence to FBI public corruption agents.

Rivera has attacked the two witnesses, who have worked for Rivera and Rubio in past campaigns.

Rubio defended their work and integrity.

“I’ve known [them]. They’ve been around in politics a long time,” Rubio said. “I’ve always had positive dealings with them.”

Rubio said he didn’t know anything about Rivera’s latest case.

“Obviously, he’s a friend,” Rubio said. “We always wish him the best.”