Hillary Clinton is now letting Barack Obama have it. Karl Rove, some think, could not have done a harsher ad on Snob-gate. She says in her latest ad that his “I don’t take money from oil companies” line is a lie, or at least an exaggeration, since no one can directly accept corporate money. (A little late, but she’s basically right.) Then, for good measure, she throws in that he voted for the Bush-Cheney energy bill.

This tells us a few things. First, Clinton thinks Obama’s brand (high-minded, honest, decent) is scuffed up and she’s going to make sure it gets permanently damaged. This is a character ad, the first one she’s used. Before learning about Snob-gate and Reverend Wright no one would have bought it. Now Clinton is hoping they will.

Second, she wants to win Pennsylvania by a healthy margin to give superdelegates something to think about. The morning after a convincing win, her refrain that Obama can’t win the big states and her argument that he can’t win working class voters will have some real oomph.

Third, she doesn’t much care if she echoes the same themes the McCain campaign is pursuing. She’s not above sinking her party in November. And if her polling (you know they poll this) says Obama is vulnerable on exactly the points the GOP is raising, then there is no reason, in her mind, to hold back.

So McCain doesn’t need his own money for an ad budget right now: he’s got Hillary’s. But if she by some miracle wins the nomination, she will be an infinitely more attractive candidate than the GOP anticipated to those critical Reagan Democrats. McCain better hope she wounds, but does not kill, her opponent. (The good news for him is that this is the most likely outcome.)