I think there are many smart people who support the Bush Admin. not because they are idiots but because of where their interests lie. I wouldn't be so quick to categorize Bush supporters as a group as beign without brains but I would question how narrow their interests might be.
If people truly looked at their "interests," Bush's support would be infinitesimal and confined to a few board rooms. I think a lot of people have too much emotionally invested in Bush and if they turn on him now they'd have to admit that in some way, they were a failure as well. My step-father knows full well that Bush is the worst president in his lifetime and will criticize the heck out of the administration so long as we stick to particular issues, but when W's name is mentioned he defends him with a vengeance (an illogical vengeance, but vengeance nonetheless). He voted for W as Gov and both times as Pres. Once called him "the greatest" president. Still, he "knows" at some level that W is not the President he once thought he voted for, but he can't bring himself to make that jump to opposition, even though he is disgusted at any number of things done by the administration. It's the reverse of the "hate bush" charge leveled at Dems, but in this case, it has a bit more truth to it.
i think a lot of people are in the same boat. they know W is one of our worst presidents but they cant swallow their pride and just admit it. also, it doesnt help that some people sit there repeating over and over "i told you so." when bush builds his presidential library, i wonder what percentage of the documents will remain classified...80%, 90%, 99.99%... or maybe all the words will be blacked out except "the", "and", "but"...