Again for me, at least, it's hard to imagine that a candidate of her high intelligence with her decades of experience in politics and obviously high level of astuticity when it comes to politic situations could believe the former. She'd be widely derided as the illegitimate candidate on both sides of the aisle and blacks and the young brought in through Obama's campaign would be two main demographics the Dems need to win who would be thoroughly alienated by this move.
Just doesn't add up...
And for me, it's about equally hard to imagine the latter. I don't think she wants to play second fiddle to anybody, and certainly not to an upstart who has shocked and I think really embarrassed her with the degree of success his campaign has had, taking him from almost out of nowhere to the nomination despite her much, much higher profile and connections and (at least initial) funding sources and so on.
Well...
I don't think so. 
There's a question after my own way of thinking, however!
And again, don't forget: there's always 2012, if he wins the nomination but loses the election, at which point he'd probably be out of favor and she'd be back with a powerful "I told you so!" argument.
I mean, really, if in fact she really believes stuff like that she can win every state from here on out 2-to-1 or that the superdelegates will risk killing the party
and losing the election because of hypotheticals about how she's more electable and dubious math and talk of popular votes and so on, is it such a stretch to think that she might be thinking in terms of a loss this year and a chance to run again (but not against him!) in 2012?
Steve