The Republicans have made much of [Kerry's]... record; the Kerry campaign is haunted by replays of the theme song from the old TV show "Flipper." Mr. Bush, however, has a far more dangerous pattern of behavior. On issues from tax cuts to foreign policy, the president tends to stick stubbornly to his original course even when changing events cry out for adaptation. His explanations seem to evolve every day, but his thinking never does.
This is how the NYT put it, in an editorial about Kerry's vote on the Iraq war resolution. I couldn't have said it better myself.