When you're this far in the game, and more Democrats think you are the stronger candidate to take on the opposition in November than your rival candidate, then you'd have to be just plain stupid to drop out after having come that far.
Yes, even with all mud slung at her, even with all the odds against her, even with everything that's gone on, at this moment more Democrats think she'd do better against McCain than Obama would. Now given that statistic, how far along we are and the fact that the ENTIRE POINT OF THE PRIMARY is to pick the strongest candidate to take on the opposition in November, if you don't think that ALONE is justification for remaining in a hard fought primary then you're likely not thinking at all.
http://www.rasmussenreports.com/public_content/politics/election_20082/2008_presidential_election/fewer_democrats_want_hillary_to_drop_outsnip
"Overall, Democrats are evenly divided as to which candidate would be a better general election candidate against John McCain.
Forty-six percent (46%) view Clinton as the stronger candidate while 44% say Obama will do better."