WASHINGTON (AP) — A person familiar with the case says an ex-aide to former Republican Sen. John Ensign is expected to plead guilty Thursday to a misdemeanor violation of lobbying law.

Doug Hampton left his job as Ensign’s administrative assistant four years ago after discovering Ensign had an affair with his wife. Federal prosecutors alleged Hampton then began lobbying the senator’s office on behalf of Nevada-based clients in violation of the yearlong ban on former employees lobbying the Senate.