"Richard Mourdock is this year's Ken Buck. Tonight's results make the Indiana Senate race a toss-up race," Democratic Senatorial Campaign Committee executive director Guy Cecil said in a release. "Tens of thousands of Hoosiers who have voted for Dick Lugar their entire voting lives are going to reject a Tea Party candidate like Richard Mourdock and support an honest, common sense job creator like Joe Donnelly." While Lugar's loss boosts Donnelly's chances, the make-up of the GOP-friendly state gives Mourdock the early edge. President Obama notched a surprise victory in Indiana in 2008, but his campaign is not expected to contend there this year. "As an officer in the U.S. Navy, Mayor of Indianapolis and a U.S. Senator for the last 36 years, Richard Lugar has served with honor and devoted his distinguished career to public service. All Americans owe him a debt of gratitude," said National Republican Senatorial Committee Chairman John Cornyn in a statement. "I congratulate Richard Mourdock on his victory tonight and I look forward to serving with him in the U.S. Senate. He has the NRSC's full support and we are committed to helping elect him as Indiana's next U.S. Senator in November." Lugar, who was first elected in 1976 and serves as the ranking Republican on the Senate Foreign Relations Committee, is the first incumbent senator to be defeated this year. His sub-40 percent tally could end up being the lowest primary total of any sitting senator in over 20 years. President Obama, who worked closely with Lugar on nuclear deterrence issues when the two served in the Senate together, issued a statement acknowledging his "deep appreciation for Dick Lugar's distinguished service in the United States Senate." The White House called Lugar's departure a "retirement" -- a euphemism for the decisive defeat he faced Tuesday night.