We have already discussed crackpot theory #1: Hillary 2012, which necessitates an Obama loss. In this theory she stays in not because she can win, but to make sure that McCain wins so she can run against him later. The downside and where the theory falls flat is the assumption that the party would forgive her enough to give her a plausible run.
Theory #2, which is plausible, is that she is staying in because the longer she stays in, the more leverage she gets. This article suggests that she will deploy that leverage to demand the Veep slot from a hesitant Barack Obama:
A person close to her, with whom her campaign staff has counseled at various points, said this week, "I think the following will happen: Obama will be in a position where the party declares him the nominee by the first week in June. She'll still be fighting with everybody -- the Rules Committee, the party leaders -- and arguing, 'I'm winning these key states; I've got almost half the delegates. I have a whole constituency he hasn't reached. I've got real differences on approach to how we win this election, and I'm going to press the hell out of this guy. ... Relief for the middle class, universal health care, etc.; I'm Ms. Blue Collar, and I'm going to press my fight, because he can't win without my being on the ticket.' "
Another major Democratic Party figure, who supports her for president, agreed: "It's not going to be a quiet exit. ... Obama has got a terrible situation. He marches to a different drummer. He won't want to take her on the ticket. But he might have to, even though the idea of Vice President Hillary with Bill in the background at the White House is not something -- especially after what [the Clintons] have thrown at him that he relishes. I believe she'll go for it."
However, several important Democrats aligned with Obama predicted that he -- and Michelle Obama -- will vigorously resist any Clinton effort to get on the ticket. Rather, Obama is more likely to try to convince Clinton to either stay in the Senate or accept another position in an Obama administration, should he win the presidency.
So let's throw in this twist: What if it's a mix of theories #1 and #2? What if Hillary wants Obama to lose, but furthermore wants the veep slot in order to ensure that loss? Just think of how Bill "helped" her and what he could do for Obama!
Furthermore consider that in Democratic circles, losers in general elections never run again (Mondale, Dukakis, Gore, etc.) While VP's in losing battles usually didn't get the stigma of "loser" on them (Ferraro, Bentsen, Lieberman, Edwards, etc.). Gore of course being a big exception to the rule, as he could have come back, being the best loser of all losing Democrats in the last thirty years.
So Hillary demands the veep slot, sabotages the Obama campaign, and sets herself up for a rerun in 2012. It's just barely plausible enough that it explains why Obama wants her nowhere near the ticket!

