Jeb Bush calls it an unbelievable scenario. Karl Rove says life on Pluto is more likely. Still, national Republican Party officials and attorneys are quietly preparing for a prospect that no longer looks inconceivable: By the time thousands of Republicans converge for their convention Aug. 27-30 at the Tampa Bay Times Forum, they will not have a nominee. "Everybody that says they've got a crystal ball about the 2012 presidential election should have their head examined," said Phil Musser, a Republican strategist supporting Mitt Romney. "There have been more loops in this race than the roller coaster at Space Mountain,...