I think you're all missing an obvious one. Michelle Obama. If her husband's successful, she's the next Hillary. I don't know what her ambitions are regarding public office, but who does?
I think her negatives make Hillary look like Betsy Ross.
Examples?
Many of her comments on the campaign trail, including, but not limited to, the "first time in my adult life" line, have come off as snobbish, condescending, and occasionally outright disdainful to the American public.
Her thesis, while not necessarily a negative in it's own right, hurts the "post-racial" image she attempts to portray.
Okay, so perhaps my statement was a bit heavy-handed, but I maintain she does have definite negatives she would have to overcome before considering a run for office herself.