That's basically what he's doing. He's criticizing Bush for liberal policies, so he's withdrawing unqualified support.
As a strong backer of George Bush in 2000 and 2004, I never gave "unqualified" support. And few in the ranks of conservatives did either. The issue is: in the political struggle for the future of America, what is to be done? I would argue that we criticize the policies we don't like, but within the general stance of support for the President. (This I did in Bush's first term, and continue now, especially with regards border soverignty.) Beyond that, George W. Bush isn't going to be elected again. So begin to work for candidates who more nearly support your values and interests.