In this context, 'dumb' bespeaks elitism. More accurate would be intellectually dishonest and lazy, but in this case that would be the pot calling the kettle black.
mbs
Chris Caldwell writes in this week's New York Press:
<quote> Dumbo One ploy that's definitely not going to work is this Gore use of surrogates to attack Bush's intelligence. Yes, Bush is slow, and I can say that-but Gore can't. Bush is dumb only for a politician; he's smarter than the median voter. So the median voter is going to watch some Al Gore shill talk on national tv about what a dope Dubya is. And said median voter is going to think: "If Gore thinks he's dumb, what does he think of me and the wife and kids?" </quote>
Doug