If Biden were to be the one, I think you’d quickly discover how little regard the left really has for him. He doesn’t have the right qualities to pull them together. Not a first banana.
+++++++++++++++++
No but he is a familiar and easily controlled banana
Such a person would not exhibit the requisite charisma and inspiring qualities to rally the Democrat base together, should Hillary bail. Biden's not the one.
Coming back to the question, I still can't think of anyone on their side who could get the job done.