If marketed correctly (it is all about marketing anyway), I think Kamala Harris might have a shot at beating Trump. One demographic that has pulled back their support for Biden are Black Americans. This might re-energize them. Also, with 2 women on the ticket (Gretchen Whitmer as VP), they also might re-energize the women's vote. You are right. If Biden stays in the race, he will lose. The Dems don't have a lot of choices this late in the game.