they couldn't legally pull a Torricellie Switcheroo the first time they pulled it so I'm not sure why the illegality of it would stop them now.
It's not a question of legality. The electors and the DEM party are on the ballot in all 50 states.
Of course, there is a question of whether enough DEMs would vote for another candidate to win the elctoral college, but that is a practical matter, not a legal one.