 On February 10, 2010, Coats confirmed that he would return to Indiana to run for the seat held by incumbent Evan Bayh in the 2010 United States Senate election.Bayh had made no previous announcements and was fully expected to run for another term, but after Coats announced his candidacy, Bayh announced his retirement on February 15, 2010.On May 4, 2010, Coats won the Republican primary over State Senator Marlin Stutzman and former U.S. Representative John Hostettler.