On its face, it makes no sense at all for Jill Carney's distaste for negative politics to cause her to run toward the Clintons, of all people, but Obama's negative attacks hurt his image worse than Hillary's do simply because she's never had any compunction about negativity or engaged in the self-righteous tut-tutting of the Obama campaign. Obama is punished for falling short of his image as an uplifting reformer because he chose to make it the centerpiece of his campaign. It's the same reason John Kerry suffered interrogations about his war-hero image, and family values conservatives are castigated for cheating.
Obama's problems are compounded by the fact that if he's not that nice, new, squeaky-clean politician at all times--and the close fight in the Keystone State will not allow him to be-- he starts to look dishonest. He's been selling Bambi-style politics, but when it comes down to it, he may become the hunter in a split second, battering Hillary with both barrels to serve his own purposes.
Honesty, of course, is his greatest advantage over Hillary. A recent poll showed him up 23 points on her in the head-to-head on that important quality, which is why he talks about Bosnia on the trail as much as possible. Americans-- left and right, to some extent--perceive him as a decent guy who's honestly interested in playing the game differently. That won't last forever. The Wright and Ayers associations, and the "bitter" incident have taken some of the shine off, and a knock-down, drag-out with Hillary will feed the creeping suspicion that the Messiah was just a snake-oil salesman all along.
Obama is going to run into the same problem Hillary ran into in the primary, once his principal rationale is weakened in the heat of this extended Democratic race. Assuming Democrats are likely too far into the process to make the switch to Hillary (though it's not entirely impossible), Obama will start flailing for a new, improved rationale right around the time the very short general election gets started in earnest.
McCain will have presented himself as a strong leader, a tested decision-maker, and an everyman capable of mingling with the small-town folks Obama has scorned. The McCain campaign, with some help from Obama, will have portrayed Obama as an elitist wimp not to be trusted with matters of national importance.
McCain's an experienced campaigner who knows himself and who is known by the American people. He will wage a new kind of campaign, with frequent town hall appearances increasing his reputation as an honest, straight-shooting guy while Obama flails for a perfected rationale, likely closing himself off from frequent questioning.
It seems to me it will become rather clear rather quickly who represents more of that "new" kind of politics Obama-maniacs fetishize. An old dog will be teaching Obama more than a few new tricks.