The only way it could work is to have everyone who is replacing Slo Jo urge their followers to vote for them via a write-in. Since ballots have already been printed and in some areas are being used even as we speak to vote, it's too late to replace Slo Jo's name on the ballots. Also, there are time restrictions on when a person (oh, say, Slo Jo) can be listed on the ballot. That time has already expired.
If they decide to run someone else, all the previously voted for Biden ballots would be...invalidated? or automatically changed to whomever the Dims decide to run? Oooh, ooh, Mistah Kahter, I see Judge Amy's first case!
Daffy Duck for president!!! (you hear that dum dum dum dumda in the background? That's Hildabeast, slugging her way to her closet, picking out that stupid purple (for royalty, doncha know) outfit for election eve. No prob with wearing it again, technically the crowd never saw her in it, so it's ok to be the sloppy second.
Daffy Duck for the Dems, 2020!
http://www.freerepublic.com/focus/chat/3894123/posts?page=713#713
In some states, one must publicly declare their intention to stand for a write-in vote before the election for a specific office.
That means filing the proper paperwork.
Michigan, IIRC, is one of those.
And, there is a time certain for that declaration to be made before the election date.
Other State’s MMV
Someone told us "Timing is everything".