Similar to what the polls said about Hillary and Trump on the last election hehe.
I speculate that Biden's running mate might be a woman. The democrats want their first woman president after their first black president hehehehe.
The only way for this is through 77 year old Biden who the democrats will make sure not finish his term.
What about some of those primary candidates, such as Elizabeth Warren, Amy Klobuchar, Kamala Harris or Kirsten Gillibrand? Personally, I would prefer someone who is energetic and popular with the youth, such as Tulsi Gabbard. He's 77 years old, and non-Hispanic white. He needs a running mate, who is young, and non-white. Someone who can attract the youth vote.