Being the "dumb" candidate has actually been a pretty good formula for Republican presidential aspirants these past few decades.Ronald Reagan was famously dismissed as "an amiable dunce" by Clark Clifford, a longtime player in Democratic politics, and the Carter White House was glad to draw him as an opponent in 1980 -- until Reagan pulled away late in the campaign and racked up a 44-state landslide. And 20 years later, the "dumb" label was affixed to George W. Bush, who still managed to unite his party around him and end up in the White House.
That said, Perry may be vulnerable to the "dumb" card in ways that Reagan and Bush weren't.
For one thing, both of them came to the race with a much firmer grip on the party. Reagan entered the 1980 campaign as the undisputed leader of the conservative wing of the national GOP, a role he'd cemented with his near-miss challenge to Gerald Ford in the 1976 primaries. Because the Republican Party was more diverse back then (with actual moderates and liberals), Reagan still had to endure a taxing primary season, but his triumph was almost inevitable: As long as the conservative wing was with him, he couldn't lose. Similarly, Bush came to the 2000 race as the overwhelming GOP favorite, the clear (and lavishly funded) choice of his party's most influential elected officials, money-men and -women, activists, interest group leaders, and media commentators. Their supporters knew all about Reagan's and Bush's intellectual reputations, they weren't going to waver...
This leads to the second problem Perry faces. When Bush was fighting off the "dumb" charges in 2000, he and his supporters could lean on a perfect talking point: the example of Reagan. See, they could say, it all worked out fine. But while Perry can play the Reagan card too, he's also burdened with the example of Bush, whose presidency most Americans still desperately want to forget.
http://www.salon.com/news/rick_perry/?story=/politics/war_room/2011/08/29/rick_perry_dumb