One on one, O'Malley would beat Clinton. He would have had most of Sanders left-wing support plus less opposition from the party establishment.
Basically Clinton is a terrible candidate who would lose one on one to most people. The only reason she's barely beating Bernie Sanders is because he's a shouty weirdo. Seriously, I love Bernie but if he could just learn to talk like a normal person, he would probably have a 20 point lead nationally and have won Iowa.
lulz
Sanders led Biden in a poll by 20+ points. Try again.