A leading watchdog calls for the Senate Ethics Committee to look into multiple mysterious payments made to the senator's mistress and her family.

Republican Senator John Ensign of Nevada admitted to an affair with Cindy Hampton, a female campaign staffer married to another staffer, Douglas Hampton, from his Senate office. Ensign then claimed that his out-of-the-blue confession was motivated by the husband’s demand for an exorbitant sum of hush money. But by confessing his transgressions, Ensign prompted widespread scrutiny of a series of curious payments he made to the Hamptons during the period he said the affair took place.

According to Melanie Sloan, executive director for Citizens for Responsibility and Ethics in Washington, because Ensign has so far refused to discuss the suspicious payments, the Senate Ethics Committee must open an investigation. “The Senate Ethics Committee should call Ensign and require him to explain the whole situation because he seems so reluctant to explain to the public what happened,” Sloan said.

A month after Cindy’s salary doubled, her son began receiving $500 a month from the National Republican Senatorial Committee for undisclosed services.

Sloan said the Ethics Committee should demand that Ensign detail the nature of Douglas Hampton’s alleged blackmail scheme, describe the process his office used to calculate a whopping payment to Hampton one month before he left his job, and explain why he left his job. “There are a lot of issues here but we don’t have a lot of facts,” she stated. “[The Senate Ethics Committee] should act on this right away.”

Ensign said his affair with Cindy Hampton lasted approximately nine months, between December 2007 and August 2008. In April 2008, as the affair reached a crescendo, Ensign increased the already hefty monthly salary of Douglas Hampton, his administrative assistant, from $13,555 to $19,679—an increase of $6,124. According to a statement issued by Ensign’s office, the payments “were equal to 12 days of unused vacation,” and therefore not a severance package or hush money.

The month after receiving the raise, Doug Hampton left Ensign’s office for reasons that remain unknown. Soon after Hampton departed, however, Ensign helped him get a job at November Inc., a campaign firm run by another former staffer. According to November Inc.’s CEO, Ensign was “supportive” of Hampton during the hiring process. When Hampton left that job in August 2008, he was promptly hired by Allegiant Air, a Las Vegas-based airline owned by a major Ensign campaign contributor. Hampton’s son, Brandon, works in the airline’s call center.

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Two months after the affair began, in February 2008, Ensign promoted Cindy Hampton to treasurer of his Battleborn PAC, doubling her monthly salary from $1,385.24 to $2,771.50. He also doubled her salary at his campaign committee, from $500 a month to $1,000. Ensign’s office claimed Hampton was raised because of an increased workload.

Yet a month after Cindy’s salary doubled, her son Brandon began receiving $500 a month from the National Republican Senatorial Committee for undisclosed services. As it happened, Ensign was the NRSC’s former chairman. Ensign’s office insisted the senator had nothing to do with the payments. “[Brandon Hampton] came to D.C. when his high-school classes were done, and it was known when he came on that it would be a temporary hire because he was going back to Las Vegas to attend college in the fall of 2008,” the Ensign office’s statement read. “John Ensign was not consulted as part of the decision to hire Brandon Hampton at the NRSC.”

While Ensign’s office frantically tamped down on mounting suspicions, the Hamptons quietly hired a personal-injury lawyer. According to Sloan, the Hamptons could sue Ensign for offenses ranging from sexual harassment to discrimination on the basis of sexual orientation. Further, the Hamptons are unlikely to allow Ensign’s accusation of blackmail go unchallenged. They will probably issue a public statement that could raise more disturbing questions about the senator’s conduct, Sloan said. But unless the Senate launches an investigation, the full truth about Ensign’s transgressions may never come to light.

Xtra Insight: The Daily Beast's Max Blumenthal: 'Sanctity of Marriage' Advocate Sen. Ensign Eats His Words

Xtra Insight: The Daily Beast's Mark McKinnon: Ensign, Get Your Sorry Ass Out of the Senate

Max Blumenthal is a senior writer for The Daily Beast and writing fellow at The Nation Institute, whose book, Republican Gomorrah (Basic/Nation Books), is forthcoming in Spring 2009. Contact him at maxblumenthal3000@yahoo.com.