Not to mention his atrocious domestic policy.
I mean, yeah he's always been a "maverick", sort of. But then again, he's still a conservative pick. I think in hind sight, the failure to veto the bill banning gay servicemen from the military really bit him in the ass the most.
Charging into Iraq is semi-forgivable. Hes far from the first leader to do something like that, and his screw-up arguably had the least impact at home of any one of them in history.
But the two images just really didn't mesh. Especially having been quoted showing support for any man or woman willing to put on the uniform for their country, and then the Iraq war vets turning into the new Vietnam War vets, and finally banning LGBT members.
Any one of them on their own would have been completely possible to ninjitsu away with a competent PR department. But for reasons known perhaps only to God, he stumbled into all of them.
Edit: thinking on it, my bet is that gore would have been basically another Jimmy Carter. Mild as milk, good intentions, and a solid record, but stymied by political realities.