Mark Edward Souder (born July 18, 1950) is an American Republican politician who was a U.S. Representative from Indiana from 1995 to 2010.During the 1980s and early 1990s, he worked as a congressional aide to Dan Coats and committee staff director. He was elected to his congressional seat in 1994. On May 18, 2010, Souder announced his resignation from Congress effective May 21, 2010, after admitting to an affair with one of his part-time female staff members.