The only way Biden leaves the race is by his own choice. He can be cajoled to leave but the party isn’t going to force him out. The question would be who would replace him and he would have a lot of say in that matter. I would say Harris and Newsome would be the two most likely picks. Personally, I think Newsome would be the right choice since he is corporate enough to please the neoiberals but forward on enough issues to not totally lose the progressives.