It seems as if it was Nancy Pelosi who finally put the pressure on Biden-the nuclear option, that is to say, threaten to invoke Article 25 of the constitution and declare the President insane, were he to refuse to step down. The man is evidently a shadow of his former self, not helped, I suspect, by Orlistat, stripping all the natural absorption of nutrients for the low-fat diet fad, assisted manfully by several bouts of facial rejuvenation surgery.
It seems the front runner and likely replacement will be Jamaican-Asian Vice-President Kamala Harris, former Attorney General of California, who during her schooldays was bussed to an out of area school to maintain the required ethnic mix in education establishments. The same policy was pursued by ILEA in the 1960s. If she has the ability to control her cackle at regular intervals she may stand a chance. If the Democrats do decide on a contest (and time is fast running out), the current Governor of California, Gavin Newsome, would be Harris' main challenger. He is described as white liberal-elitist, wringing his hands of that state's drug problems and out of touch with working-class people of all ages. An outside contender would be Gretchen Whitmer, Michigan's stalwart Governor, who has a reputation for getting things done, though I can't see two women on the Democratic ticket, so she may have to wait for another day.