Spoonz Red E
Very well known Exeweb poster
That works at Presidential level with the VP taking over.Googling it, The Democratic Convention is on 19th August, Doesn't give them long to get a replacement if Biden agrees to stand aside. Isn't there a 25th Ammendment? That can put the wheels in motion?
It's not a party rule.
There are probably party rules where someone can be removed - misconduct etc. but this would be counterproductive in this case as it's not just Biden but all his current delegates that have to be won over.