Obama is overexposed. And what's worse, he himself is seeking the overexposure based on the mistaken (and somewhat grandiose) premise that he can charm the American people into accepting a pork package that, as Mitt Romney has cogently put it, will stimulate nothing but government growth.
Many presidents take office with overly optimistic beliefs of what they can achieve, based on their past experiences. George W. Bush, for example, had made common cause with the Democrat Lieutenant Governor of Texas, Bob Bullock. Because of that, he seemed honestly to think that he could bridge the partisan divide in D.C. He courted Teddy Kennedy, renamed the Justice Department Buildling in honor of RFK, and reached out and out and out. You see where it got him.
Barack Obama's analogous mistake is thinking that he has established a rapport with the American people, and that they will rise up to support his package just because he tells them to. He's wrong. Many Americans haven't actually decided what they think of him yet. He's on probation (as is any new president at this point in his term -- especially a largely unknown one, like Obama).
It's dangerous to believe that one is uniquely equipped to woo the other side -- as George W. Bush learned. It's even more dangerous to believe that one has earned the trust and respect of the American people, even before achieving anything as President (and little of political substance before that).
Finally, the main problem for Obama is that the pork bill is a pig. And as a fast-rising politician pointed out over the summer, that means you can put lipstick on it with some highfalutin rhetoric . . . but it's still a pig.