The man's a neurosurgeon - he's not dumb, he's just faking it to appeal to the more cretinous reaches of the Republican electorate, which is even worse.
Trump's a fool, and appeals to the other fools, but at least he probably believes in most of the shit he speaks without actually thinking about it.
Carson knows better, and rather than have principles he's talking shit simply for a tilt at power - despicable.
O.