Mitt Romney

Most of the time, a smile on his face will last one or two seconds and not much longer. A smile lasting more than four seconds will almost always be either a sign of real ecstasy or simply political calculation. Watch him as he stands on the debate stage, smiling in the background as one of his rivals is fielding a question (especially a tough one). The social smile so readily adopted by Romney is, in truth, the mark of a businessman, which is of course part of his impressive resume. That's not to suggest that Romney isn't happy; he probably is. But the degree to which his smiles seem manufactured is more reminiscent of Hillary Clinton's smiles than those of any other major candidate.