With the May 8 Republican primary approaching, Indiana state Treasurer Richard Mourdock has picked up another high-profiled endorsement in his bid to unseat incumbent Sen. Dick Lugar.In a Tweet, former Republican presidential candidate Rick Santorum announced he is backing Mourdock, and wants Hoosier voters to do the same."I encourage Hoosiers to help GOTV for @RichardMourdock," says Santorum. "If I lived in Indiana he'd have my vote in Tuesday’s #INSen race."The endorsement from the former Pennsylvania Senator piles on more bad news for Lugar, who is trailing Mourdock by 10 points in a new independent poll released Friday. A review of U.S. Senate elections shows that if Lugar is defeated, he will become just the first six-term Republican Senator to fail in his renomination bid in over a century