All politicians make gaffes, yes. The enthusiasm with which the gaffes are reported, repeated, and presented as evidence for the gaffe-producers' lack of intelligence, however, varies a great deal. Many people are convinced that Dan Quayle and Sarah Palin are stupid, largely as a result of the reporting of their gaffes. Is it possible that an equally relentless drumbeat of '57 states' and other Obama gaffes (of which there are a great number, as I presume from your claim you'd concede) would have produced a similar impression of Obama? That, I think, is the point: the popular press and mainstream TV choose which politicians are going to be perceived as stupid. We're fools if we let them do it without attempting to counter it.