Quote from Rearden Metal:
People nearly always vote for the candidate they'd rather have a beer with. Hil-dog just isn't that kind of candidate, hence she has no chance. It's that simple. I wouldn't even be surprised to see her get knocked out in the Dem primaries.
This doesn't explain the Nixon re-election landslide, amongst other election results. Everyone hated his guts, but they at least respected him for being competent (outside of Vietnam), whereas Agnew was viewed as a near-commie menace and not a heavyweight. They basically held their nose and voted for tricky Dicky. Voters will generally prefer someone they dislike but who they think has sufficient stature for office, versus a likeable but unsound lightweight.