Why is Hillary staying in?

Here are a few theories:

1. She wants something. Maybe a spot on the ticket, maybe an appointment, but she definitely wants something, according to this theory. Why else remain in when it appears highly unlikely that she will wind up winning the nomination? She's trying to maximize her leverage to make a deal. Then again, if her rationale for continuing her campaign is so cynical, why is she still holding out? This is a stock whose best time to sell was a while ago...actually, had she bowed out after Wisconsin she would have been able to write her own ticket (so to speak) and Obama would have been invincible going forward. If her understanding of the situation is so clear-eyed then what is the benefit to continuing along this course?
2. She's in denial. This has been my theory for some time. Clinton seems like the sort of person who mapped out her destiny some time ago. She can't accept that the dream is dead, so she's stubbornly persisting on this course in hopes that a miracle will become manifest. There is some synchronicity here with some other things--her personal life, obviously, reeks of denial, and there was that Bosnia flap, among other things.
3. She's trying to kneecap Obama. Proponents of this theory argue that Clinton is trying to add legitimacy to right-wing attacks (Bill Ayres, por ejemplo) in order to make sure that McCain wins so that Clinton can run again in 2012. I doubt that she has consciously decided to follow along this path, and if this is the goal of the Clinton campaign at this point she's not been very artful about it. As I see it, her political career is pretty much over--she's made too many enemies with her rough-and-tumble tactics, she's proven she's not a team player, and she's proven a prisoner of the conventional wisdom. She's unlikely to ascend any higher than she is now. If she somehow won the nomination, the party might just rally around her because they want to win, but if she doesn't get the nomination, goes scorched earth and Obama loses she's going to be getting much of the blame, and she'd probably be primaried in 2012. She has to be smart enough to know that, though there is some evidence that she's willing to turn off the reasonable part of her brain under some circumstances.
   

That's all I've got. Still think it's option two. I suppose she still honestly thinks there's a way for her to win this thing, but at this point that's indistinguishable from #2.