@Kitiem3000 probably knows better than I do, but let me throw this perspective out there anyways. In my view, a 9/11-akin terrorist attack in 03, instead of 01, hurts George W. more than it helps him. With it having happened so early in his Presidency, he's less to blame than the former administration would be. But if it happens so close to the end of his first term, I could see Democrats making the argument that Bush was weak and incompetent, unable to protect the US from terrorism. How effective that argument would be is subject to speculation, but I could see the Democrats potentially riding it to victory in 04. Although probably not with the same ticket as OTL, maybe Wesley Clark manages to nab the nomination?