From Joe Klein's very good column about how Bill is spoiling Hillary's campaign:
It is entirely possible that Hillary Clinton will win this nomination. One on one, she simply seems stronger than Obama. But two on one, she seems weaker. And if she wins the nomination, you can bet the co-presidency question will be front and center in the general election. It is, therefore, vital that she address it now. She's got to say something like, "Bill's a fighter, and he got a little too feisty these past few weeks. He knows that, and he's decided to return to his charitable work for the duration of the campaign. I will continue to run as I will govern—on my own." [Emphasis added.]
Hmm. Looks like they'll need to come up with something else to keep Bill busy.