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U.S. Senate candidates running in the GOP primary, Sen. Richard Lugar, R-Ind.,and Richard Mourdock, left, participate in a debate Wednesday, April 11, 2012, in Indianapolis. (AP Photo/Darron Cummings, Pool)

Indiana Sen. Richard Lugar loses seat

Richard Lugar, the longest-serving Republican in the Senate, was defeated May 8 as Indiana Republicans chose state Treasurer Richard Mourdock over Lugar as the party's nominee.