In fairness, Obama's problem is that he's put himself in a box. He's campaigning as a straight talker, which means that even small, routine panders open him up to attacks as a hypocrite. He's campaigning as the guy who can bring us together, which means that even a modest bit of trash talking provokes squeals from the press corps. He's campaigning as the candidate of fresh, bold ideas, which means that any time he presents a sensible but routine policy idea he takes a hit for being the same old wine with nothing but a new label on the bottle. And he's further hurt by the fact that Hillary Clinton's campaign is brilliantly ruthless at taking advantage of all this.
But politics is what it is, and Obama is in a box whether he likes it or not. When you're selling yourself as the candidate of idealism, small deviations disappoint your followers more than big deviations from more conventional candidates. This is why idealistic candidates virtually never win. So far Obama hasn't figure out a way to escape this box, and he doesn't have much time left.