I would expect a lot of blacks to stay away from the polls if Elizabeth Warren is the VP. They have doubts about Joe right now. Choosing that old white lady as VP? When he could have chosen Stacy Abrams? It’s not going to play well at all.
2020 is a Demagogic Party referendum on the Old Guard (mainly but not exclusively white people). Getting rid of Joe and another old white corrupticrat clears the way for 2024. Oh, and if you're not really black, you won't vote for Joe, so there. :^)