But I think the real reason is simpler: as with blogosphere conservatives, mainstream conservatives are mostly urban sophisticates with a libertarian bent, not rural evangelicals with a social conservative bent. They're happy to talk up NASCAR and pickup trucks in public, but in real life they mostly couldn't care less about either. Ditto for opposing abortion and the odd bit of gay bashing via proxy. But when it comes to Ten Commandments monuments and end times eschatology, they shiver inside just like any mainstream liberal. The only difference is that usually they keep their shivering to themselves because they want to keep everyone in the big tent happy.
But then along comes Huckabee, and guess what? He's the real deal. Not a guy like George Bush or Ronald Reagan, who talks a soothing game to the snake handlers but then turns around and spends his actual political capital on tax cuts, foreign wars, and deregulating big corporations. Huckabee, it turns out, isn't just giving lip service to evangelicals, he actually believes all that stuff.