A memorandum from a polling firm says U.S. Sen. Richard Lugar, R-In., is set to lose his seat to Indiana State Treasurer Richard Mourdock in the upcoming Republican primary, according to a recent survey of 500 likely voters.Global Strategy Group finds the race between Lugar and his Tea Party challenger is tightening with his initial 12-point lead cut in half since October. The memo notes that the six-term Senator has outspent Mourdock by $2 million, but is only ahead by a 45 percent to 39 percent margin."After more than 30 years as Indiana’s Senator, Richard Lugar is fighting for his political life," the memorandum reads. "Despite spending millions, Lugar continues to lose ground in the Republican Primary and faces the very real possibility that on May 8, he will be out of a job."The survey also shows a high level of disapproval for Lugar's job performance among voters with negatives at 50 percent, and 7 in 10 saying they are either undecided or that there is a reasonable chance that they will support another candidate.For weeks, political observers have paid close attention to the primary as Lugar faces a serious challenge from the right. Last week, the Marion County Election Board disqualified Lugar's residency and ruled he is ineligible to vote in this upcoming re-election bid, meaning the longtime lawmaker will have to establish new residency.