The recent poll that showed Sanders ahead of Clinton in New Hampshire also showed Biden with 9%, even though he's not a declared candidate.
I sense that if Biden jumped into the race within the next few weeks, that he would immediately siphon off about 1/3 or more of Hillary's support.
He'd probably rise to 25% within a couple of days of his announcement.
And just about all of that would come from o'er-the-Hillary.
I wonder if Biden will call tin Lizzie and ask if she'd consider being his Veep pick? And campaigning with him as such.
That would take some wind out of Bernie's sails...