A onetime aide to Sen. John Ensign (R-Nev.), whose wife had an affair with the senator, was indicted Thursday over accusations that he lobbied Ensign and his staff in violation of federal conflict-of-interest laws.

Douglas Hampton is charged in connection with lobbying he did on behalf of a Las Vegas airline company and an energy company. Federal law prohibits a senior Senate aide from lobbying the Senate for one year after terminating employment.

When Hampton found out about the affair between his wife, Cynthia, and the senator, Ensign helped line up jobs for Hampton with campaign donors.

According to the indictment, Hampton lobbied on behalf of a low-cost airline carrier in Las Vegas, Allegiant Air, and for the largest electricity provider in Nevada, NV Energy.

Hampton’s attorney, Dan Albregts, did not immediately respond to messages seeking comment. A call to Ensign’s office was not immediately returned.

The affair with Cynthia Hampton sidetracked the Republican senator’s political career, with Ensign announcing this month that he would not seek a third term.

Ensign has said the affair began during a rocky time in his marriage in December 2007 and continued until August 2008. Cynthia and Doug Hampton left their jobs with Ensign in May 2008.

Ensign came under investigation by the Justice Department, which focused on whether he conspired with Hampton to violate the lobbying restriction.

In December, the department disclosed to the senator that it no longer viewed him as a target in the probe.

On behalf of Allegiant, says the indictment, Hampton sought the assistance of Ensign and a legislative aide to Ensign to persuade the U.S. Transportation Department to reconsider its position on a fuel surcharge pricing issue. Hampton allegedly sought the assistance of Ensign and his staff to help schedule a March 2009 meeting involving the secretary of transportation and executives from the airline company.

On behalf of NV Energy, the indictment says, Hampton sought the assistance of Ensign and his chief of staff to expedite the release of a U.S. Interior Department environmental impact statement regarding a company coal-fired power plant.

— Associated Press