Re: Matt's post, here.
There are many answers, but this is my theory, which I mentioned in a column on Rudy's unexpected allure among conservatives when up against the more palatable-on-paper McCain:
McCain has an uncanny ability to exude disdain for large parts of the conservative base despite agreeing with them. Rudy has an uncanny ability to exude respect despite disagreement.
McCain gets contempt from the base because the base feels something of the same coming from him.