Seriously I'm begging people to actually look at any polling data in their wishcasting. Kamala Harris dominates all hypothetical primary polling.
Even just ignoring the hypothetical polling, she has all the natural structural advantages too. She's the sitting vice president. She is the only one that will have quick access to Biden's campaign coffers. She has a developed internal party base. And the actual people making this decision - the delegates - likely are predisposed to her more than even the hypothetical polling.
And what's doing most of the heavy lifting- she has name recognition.
If Biden withdrew, in all likelihood it would be her.