If 9/11 had happened this year instead of 2001, Bush would (probably) have won slam-dunk re-election.
First off, Bush could simply blame all America's problems (sinking economy or whatever) on the attack.
Second, in times of war, Americans lean to the right, and the Republicans are more pro-military than the Democrats.
And America would have been less isolated; Iraq War #2 would have happened first, then our invasion of Afghanistan. While the rest of the world objected to Afghanistan, they didn't object as loudly, and also acknowledged that we had a pretty good reason to be there. Less-offensive offensive comes after more-offensive offensive, thereby partially mollifying world opinion.
But don't take my word for it, this is all just supposition.
Edit: for my part, my opinion would be the same. Our invasions of Afghanistan and Iraq would still have occurred, and I think both invasions were the right thing to do.