If Kerry wins Ohio in this scenario but somehow loses New Hampshire, I'm not sure that I see him winning the popular vote. He won NH by 9K votes and lost Ohio by about 120K votes. Get Kerry over the hump in Ohio and somehow lose ground in New Hampshire, and I still don't see the popular vote changing, as Bush won it by over 3 Million.
But as for what this would mean, well, obviously there would be renewed pushes for reform of the EC. As for Bush himself, I think in his post victory appearances he would stress national unity a bit more than the ideas of Freedom Diplomacy, and maybe it might push him to further heresies against Conservatives, thereby sinking his approval rating very fast. Remember, Bush's approval rating was solid and normal until Social Security Reform alienated his fastest growing support group, seniors (Bush lost the senior vote in 2000 but won it big time in 2004), and his approval rating was passable until the right wing of the GOP freaked out over immigration reform in 2006 and started calling him "Jorge Bush". On foreign policy, Bush's second term was actually moderate in action but bombastic on rhetoric, as Syria and Iran's nuclear programs were not attacked despite the calls for the administration to do something about them, and the Russian attack on Georgia was not answered; this is most likely because of the ascendancy of the Realist faction in the State Department, many of which had ties to the Vulcans, rather than the Neoconservatives, who were somewhat sidelined leading up to the departure of Rumsfeld.