Technically, those voting for Biden are voting for the Electors selected by the Democratic Party. With the Electoral College, people are voting for those electors, not directly voting for Biden.
The Democratic Party would have to choose their candidate to replace Biden.
@GregRubini@dmills3710 Given how soon the Election is from now, you could count on them not making this choice before the Election.
They would do it after the Election, so people wouldn’t even know who they were voting for as President. They would have to do it by early Dec, before Elector’s deadline.