Republican presidential candidate and former Massachusetts Gov. Mitt Romney, left, meets with former President George H.W. Bush and Barbara Bush to receive their endorsements Thursday, March 29, 2012, in Houston. (AP Photo/Pat Sullivan)

Photo by: Pat Sullivan

Republican presidential candidate and former Massachusetts Gov. Mitt Romney, left, meets with former President George H.W. Bush and Barbara Bush to receive their endorsements Thursday, March 29, 2012, in Houston. (AP Photo/Pat Sullivan)