Mitt Romney committed a candidate’s error in Thursday night’s debate, opening himself to a comedian’s well-placed put down. As applause swelled during introductions at CNN’s Arizona debate, the sometimes-stiff Romney tried a quip: “As George Costanza would say, when they’re applauding, stop!” Actually, it was Jerry Seinfeld’s line. But actor Jason Alexander, who played George Costanza, hit back with a tweet that focused on Romney’s flip-flop from moderate Republican governor of Massachusetts to very conservative presidential campaign. In Alexander’s own words: “Thrilled Gov.