This story was written by Manu Raju and Victoria McGrane
Cindy Hampton once held the keys to John Ensign's heart.
Now she might hold the key to his career.
Doug Hampton - Ensign's former chief of staff and the husband of his mistress - has called on the Nevada Republican to resign, saying that he's guilty of both sexual harassment and wrongful termination.
But to make those charges stick, Cynthia "Cindy" Hampton herself must step forward and accuse her former lover and longtime employer of making unwanted advances or creating a hostile work environment, lawyers and ethics experts say.
And so far, she is the only participant in the love triangle to remain silent on the matter.
"The harassment claim has to come from the person harassed," said Stan Brand, a congressional ethics expert and former general counsel of the House. "I don't think the Senate Ethics Committee or anybody else in the Senate can begin an investigation of that nature without a complainant, nor should they."
Ensign appears to have survived the initial stages of his sex scandal, telling the Las Vegas Sun Monday that he intends to remain in office and run for reelection in 2012.
But his behavior has frustrated his Republican Senate colleagues - asked Tuesday whether he'd support Ensign in 2012, Senate Minority Leader Mitch McConnell (R-Ky.) said Ensign "will have to speak to those issues himself" - and the possibility of a contentious and embarrassing civil case still looms.
It's just not clear which kind.
Ensign's behavior in the Hampton affair so thoroughly blurred the lines between sexual, familial, professional and financial boundaries that experts are at a loss to figure out what kind of legal or ethics case Ensign could face if his former mistress pressed one - or if the Senate ethics panel decides to go ahead with its own probe.
"I've never had a case like that," said Washington lawyer Lynn Andretta, who mediates sexual harassment cases in the District of Columbia.
In a two-part television interview with a Las Vegas Sun columnist last week, Hampton accused Ensign of asking him to quit his high-paying job on the Senate staff last spring to help cover up the affair - and to avoid the unpleasantness of having the two men work side by side.
He went on to claim that Ensign allowed Cindy to keep her job as Ensign's campaign treasurer for weeks longer - but used her employment as "leverage" to continue the affair.
While the Hamptons have legal counsel, neither of them has filed a lawsuit or an ethics complaint yet - and Hampton has refused to say what the couple plans to do.
In the meantime, the nonpartisan Citizens for Responsibility and Ethics in Washington has asked the Federal Election Commission, the Justice Department and the Senate Ethics Committee to probe the allegations and the distribution of nearly $100,000 in gifts from Ensign's wealthy parents to the Hamptons.
"Given that Sen. Ensign conducted an affair with a campaign employee who is married to a member of his office staff, and that both individuals were terminated, apparently for reasons related to the affair, the Select Committee on Ethics should immediately open an investigation into this matter," CREW's complaint said.
"It's one thing to be a creep. It's another to be a harasser, to abuse your position of power," said former federal prosecutor Melanie Sloan, CREW's executive director. She contends that there are enough questions swirling around Ensign to warrant an ethics probe, pointing out that the Ethics Committee can investigate without Cindy Hampton making a formal complaint.
And if the Ethics Committee were to do so, she said, it could force both Hamptons to testify under oath.
"The Hamptons obviously don't look wonderful here either, neither one. Bt they're not the public figures," she added. "Really every other senator - expect for maybe David Vitter - must be cringing from the humiliation of it. It looks bad for all senators when a senator behaves like this."
Ensign has denied that he harassed his mistress, claiming that the affair was entirely consensual. And Ensign has accused Doug Hampton - once one of his best friends - of trying to shake him down.
Calls to lawyers representing both Ensign and the Hamptons weren't returned. The Senate Ethics Committee refused to comment.
Under local, state and federal law, employers are not allowed to use the threat of termination to extort sex or other personal favors from their employees.
The Ethics Committee has three legal paths for investigating allegations of harassment or wrongful termination: Title VII of the 1964 Civil Rights Act, Senate Rule 42 and the Congressional Accountability Act of 1995, a law passed in the midst of the Bob Packwood scandal. Packwood, a Republican from Oregon, resigned from the Senate in 1995 after the ethics panel voted to recommend his expulsion based on allegations that he had harassed more than 10 women, including staffers and campaign workers.
It remains unclear whether either of the Hamptons was actually terminated - and if so, why.
If Cindy Hampton was fired because she refused to continue the affair, that would be a clear case of what lawyers call "quid pro quo" sexual harassment, in which an employee suffers an employment action - firing or demotion - for refusing to submit to the unwelcome sexual advances.
But experts say the charge could also apply in cases where a sexual relationship started voluntarily - or possibly if Doug Hampton's career was threatened.
"Some courts have made clear that supervisors can't basically date an employee and then, upon their breaking up, fire them," said Fatima Goss Graves, senior counsel with the National Women's Law Center.
Sexual harassment can also come in the form of a "hostile working environment," which would include conduct - including but not limited to sexual advances - that makes an employee so uncomfortable she has to leave her job, even if she isn't technically forced to by the supervisor.
GOP senators rallied behind Ensign when he returned after initially admitting the affair. But as McConnell's response indicated Tuesday, that support has become increasingly tepid.
Sen. Lindsey Graham (R-S.C.) said an investigation into Ensign "isn't high on my list" of priorities, adding, "I guess if it got in the land of a crime, it'd be a problem - but I don't see any evidence of that."
Like most Republicans, Sen. John Thune (R-S.D.) - who took Ensign's spot as Republican Policy Committee chairman - sounded uneasy about the situation and what else may be coming down.
"I think up to now, he's done a good job of dealing with it," Thune said.
"I don't know what else may be out there, but I'm just not prepared to make any comment about that. I think, you know, this thing will play itself out, and he'll do the right thing. I have that confidence."
But it's far from clear what Republicans think the right thing is. Some Republicans privately predict Ensign might have to step down if the allegations of sexual harassment are proven to be true.
Glenn Thrush contributed to this report
By Manu Raju and Victoria McGrane