Hampton said he was not advised by the Fellowship to cover up the affair, but instead to "be cool." He said they felt they needed a more powerful voice to confront Ensign, and reached out to C Street resident and conservative leader Sen. Tom Coburn, R-Okla.
"'We need help. We're not big enough,'" Hampton said, recalling his conversation with the Fellowship. "'[Ensign] is a United States Senator and so even though we're friends, we're close, we're brothers in Christ, we need power to confront this: Sen. Tom Coburn, the hit man."
Hampton said that on Valentine's Day 2008, the C Street leadership and Coburn helped him confront Ensign.
"Tom really kind of takes the helm," Hampton recalled. "Oh, he's smoking. He is one upset man. ... And then John kind of breaks down, [saying] 'I made a mistake, I really screwed up.'"
Hampton provided "Nightline" with a letter, which he says the group at C Street forced Ensign to write and send to Cindy, ending the relationship.
"I used you for my own pleasure...," Ensign wrote. "... God never intended for us to do this."
But according to Hampton, within hours after writing the letter, Ensign called Cindy.
"I mean he is just livid," Hampton said of Ensign. "[He said], 'They made me write a letter, but it's not how I feel. ... Doug has exposed me.' As though somehow I'm the bad guy in this."
When Hampton saw Ensign the following weekend, Hampton said the senator opened up to him about his feelings for wife Cindy.
"He's in love with her," Hampton said. "[Ensign said,] 'I know what was said, and I'm not going to apologize for how I feel. Not only am I going to pursue the relationship, you can't work for me anymore.' ... He almost said it like, you've made me uncomfortable."
Hampton said he believes Ensign abused his power by pursuing the affair.
"He took advantage of his power and his position," he said, though he admits Cindy isn't blameless for participating in the relationship.
"I'm not saying that she wasn't struggling with her own feelings and her own attraction to John and her own demons," Hampton said.
Cindy Hampton would not confirm or deny her husband's allegation that Ensign took advantage of her, but the watchdog group Citizens for Responsibility and Ethics (CREW) in Washington, has asked the Senate to investigate whether Ensign is guilty of sexual harassment -- a violation of congressional ethics rules since Cindy was working for Ensign at the time the affair began.
"Did Sen. Ensign sexually harass Cynthia Hampton by conducting an affair with his employee?" asked CREW's executive director Melanie Sloan, in an interview with "Nightline." "And then, did he violate sexual harassment law by firing Cynthia Hampton and her husband when the affair ended?"
By April 2008, Ensign had fired both Doug and Cindy Hampton. But not before what Hampton saw as one final humiliation.
"He called me and said you need to come back here I need to throw you a party. If you don't come back here and let me throw you a party, people will suspect something," Hampton said.
Hampton said Ensign presented him with a gift at the going-away party -- a crystal replica of the Capitol with an inscription that reads: "To the best AA on Capitol Hill."
Days later, the Hamptons received a $96,000 check made out to Doug, Cindy and two of their children from Ensign's father -- a wealthy casino mogul.