not really comes down to democrat party leaders to make that...

not really

comes down to democrat party leaders to make that decision .....(or avoid making that decision which is a real danger ) .....then comes down to the electoral college themselves to choose whether to follow that or not

the whole thing is made a lot easier if Biden chooses not to run (and does it soon )
many possible candidates but liekly one of the dem governors

RFK is not a possibility at all