The first-term Democrat conceded that one of the affairs began as he was running on a family values platform to replace Mark Foley, a Republican who resigned amid revelations that he sent lurid Internet messages to male pages who had worked on Capitol Hill as teenagers.
Mahoney, 52, apologized to his wife, his daughter and his constituents, even as he maintained he hadn't been hypocritical.
"I can understand why people would feel that way and for those people, all I can say is, 'I'm sorry I let you down,"' Mahoney said in his first set of interviews since news broke this week that he had a sexual relationship with Patricia Allen, 50, whom he met while campaigning in 2006.
Allen went to work for Mahoney's congressional office, then his campaign. Mahoney said she was fired for performance issues, not because of the affair.
Allen threatened to sue Mahoney for sexual harassment, and they reached a settlement to avoid a public airing. Her payout came from Mahoney's personal accounts, not from campaign funds or federal dollars, he said.
Allen has not returned repeated telephone calls.
Mahoney also acknowledged he had an affair with a high-ranking Martin County official in his district around the time he was lobbying the Federal Emergency Management Agency to give the county a $3.4 million hurricane clean-up reimbursement. The funds were awarded last year.
He insisted, however, that he did nothing more for Martin County than he did for others in his district.
Mahoney confessed to "multiple" other affairs, though he wouldn't say how many.
"You're asking me over a lifetime? I'm just saying I've been unfaithful and I'm sorry for that," he said.
The multimillionaire venture capitalist maintained a distinction between his behavior in office and Foley's, though he wouldn't specify.
"With respect to the former congressman, I think that his situation is different from my situation," Mahoney said. "I don't want anybody to misinterpret that as me saying that somehow I'm more proud or whatever. I'm not saying that at all."
Foley was cleared of criminal wrongdoing and left Congress to go into real estate.
The FBI has contacted Mahoney as part of an investigation into whether he hired Allen to keep her quiet about the affair and whether he showed any preferential treatment to Martin County in exchange for sex.
Mahoney said he welcomed the FBI probe and has no reason to be concerned. He has called for his own investigation of his conduct by the House Ethics Committee, as has House Speaker Nancy Pelosi, though the inquiry may not be completed before the Nov. 4 election.
In a statement Friday, the ethics committee said it was reviewing the matter and would interview Mahoney and others.
Mahoney, whose district leans slightly Republican, said he will remain in the race. He insisted he did not violate his oath of office and said he takes pride in his record, if not his personal life.
"We did go to Washington and we got rid of the meals, the trips, we brought more transparency," he said.
That push for openness did not extend to his personal life. He said he settled the case with Allen because "whether you prevail right or wrong, at the end of the day, you're living in a glass house of public opinion."
"I was ashamed and did not want it to come to light, no doubt about it," he said.
All told, according to Mahoney's attorney Gary Isaacs, the congressman will have spent $141,903 to resolve the Allen matter $61,903 to Allen; $60,000 to her attorney; and $20,000 to his own attorney.
Mahoney said he told his wife about the affairs "months ago," and hoped voters would forgive him and judge him on his work in office rather than his personal failings.
"I do feel like I let them down," he said. "I just hope that they can understand I'm a human being. I never presented myself as being perfect."