I'm not quite sure he's making that point.
It seems to me he is more saying;
Imagine for a moment all the critisms of Bush common on the left are true - he is overly religious, dumb, and arrogant. He is still the candidate best suited to defeat the forces of Islamism, which are almost the antithesis of everything the Left claims to be for.
Or to paraphrase Churchill:
"He's the worst candidate... except for all the others."