I would watch for a Biden/Warren ticket riding to the rescue a the convention. The Democrats know Bernie can’t win. B/W would energize their base like no one else to the point that they could well take it. They certainly will if the GOP has their way and pushes Trump and Cruz aside.
If he fights the election over single payer, I think he will win.
Whoever is at the top of the Democrat ticket, the VP candidate will be the minority next in line for POTUS. Warren (66), Hillary (68), Sanders (74) and Biden (73) are all old. The Democrats will choose a younger minority to interest minorities and millenials in voting. Without a minority on the ticket, Dems may have trouble turning out the Hispanic and African American vote.
My prediction is the VP will be Julian Castro (41) who is currently HUD secretary and previously served as Mayor of San Antonio. The Democrats will want to play to the rapidly growing Hispanic population and counter a GOP ticket with Rubio or Cruz in the top or second spot.
If not Castro, the VP nod will likely go to Cory Booker (46) the black Senator from New Jersey and former mayor of Newark or Deval Patrick (59) the black former governor of Massachusetts. Kamala Harris (51) black attorney general of California or Attorney General of the US Loretta Lynch (56) are potential black female VP candidates.