Hannity is the king of FOX. He wants anyone but RP in the Republican party. It would kill his show to have a Repub against his own position on the war on terror and make him look bad to the reactionaries who would turn on him. His ratings would plummet and his position would look foolish.
Hannity and Rush thrive when Clinton is in power. You get to criticize him and uphold the Rep talking points, but when a Rep is in power like Bush you have to be on the defensive 24/7, and if he gets a Rep who is against his policies he has to defend himself from Reps and Dems with no constituency to push his talking points while demonizing everyone. He knows it and is afraid.
He's a great American in the worst kind of way.