The same day as the Transportation Department meeting, Mr. Ensign and Mr. Gallagher had lunch in the Senate Dining Room, with Mr. Hampton and Mr. Lopez joining them. Mr. Hampton also set up meetings for Allegiant with five other senators on Capitol Hill, including Mr. Coburn.

Mr. Coburn said he realized only when asked about it that his meeting with Mr. Hampton might have violated the one-year lobbying moratorium. “It was wrong,” Mr. Coburn said.

Allegiant Air and November Inc. also said they were unaware of any possible legal issues until asked recently, and said they would consult their lawyers to determine if corrective action was needed.

Mr. Slanker, at November Inc., said that if his company was part of improper lobbying efforts, “I’m going to make it right.” The whole situation, he added, “makes me sick to my stomach.”

Going Public

Months after Mr. Hampton discovered the affair, he and his wife began seeing a counselor to salvage their marriage. But Mr. Hampton said he became increasingly embittered toward Mr. Ensign over the “destruction” the infidelity had caused.

By July 2008, Mr. Hampton said he was worried about his finances, since the senator had helped him get only two clients. The next month, Mr. Hampton secured a full-time position at Allegiant Air that paid as much as $225,000 a year. But he said he still felt he was in a precarious position because of his reliance on the senator for access in Washington. “I couldn’t keep living a lie,” he said.

So in April, he hired a lawyer, Daniel J. Albregts of Las Vegas. In an interview, Mr. Albregts said he believed the Hamptons might have a civil claim against Mr. Ensign over their dismissals from his staff and the consequences for their family.