Well, he was a flip flopper on a lot of things, so maybe he would have later voted for funding of the military effort or something like that and seen it used against him.
I think he might have had his best chance in the election had he decided to shift right on cultural issues to try to win back some of the '96 Clinton states that flipped against Gore in 2000 (like Kentucky, West Virginia, Arkansas, Louisiana, or Tennessee). In 2004, all of those states went against him by more than they did for Gore, and that was mostly because Kerry really didn't take them all that seriously and pumped a lot of resources into swing states. Those states in 2004 were still excessively Democrat in terms of voter registration, and were likely more winnable than some may have thought. The voting margins in those states were volatile for most of the 2nd half of the 20th century, after all.
For Bush's part, I think Bush would have done a lot better in 2004 had he ran a more Midwest focused campaign. His campaign was essentially a Sunbelt project, based around ginning up suburban turnout in the South and Southwest. On cultural issues I think he could have competed a lot more strongly in the Upper Midwest and probably could have taken Wisconsin. I think Minnesota and Michigan were also winnable. If one compares Bush's 2004 figures with McCain's in 2008, there were areas in Pennsylvania actually that swung to McCain, believe it or not, and I think that Bush could have won PA as well had he anticipated some of the issues that brought this about (for example, taking a harder line on the side of coal production).