FILE - In this April 12, 2014 file photo, the five candidates seeking the GOP nomination to run for the U.S. Senate seat being vacated by the retiring Democratic Sen. Tim Johnson, from left, former South Dakota Gov. Mike Rounds, state Rep. Stace Nelson, Sioux Falls physician Annette Bosworth, Yankton attorney Jason Ravnsborg and state Sen. Larry Rhoden, participate in a debate in Pierre, S.D. The five will face off again in a live television debate Thursday, May 15, 2014, in Vermillion, S.D. (AP Photo/Capital Journal, Nick Lowrey, File)