Republican presidential candidates Romney and Perry participate in the Reagan Centennial GOP presidential primary debate in Simi Valley

Republican presidential candidates Mitt Romney and Rick Perry participate in the Reagan Centennial GOP presidential primary debate at the Ronald Reagan Presidential Library in Simi Valley, California September 7, 2011. Republican rivals Perry and Romney exchanged sharp jabs over who has the better job-creating record on Wednesday in a presidential candidate debate that featured the anemic U.S. economy at center stage. REUTERS/Mario Anzuoni (UNITED STATES – Tags: POLITICS)