I think it’s a bluff to try and sway wavering republicans and maybe a couple democrats.
As this is being floated by Sissy Sheldon from RI -- who is a loon, but a reliable loon in the loop -- it's clearly part of instructions from Schumer/Pelosi to throw some meat to the nutroot base.
Sure they would love to peel back Donnelly and ManChin. They've probably given Heidi enough cover to stay home and vote 'No'.
But Donnelly is going to lose either way, Heidi is probably going to lose, and ManChin will be close, and he'll be under a lot of pressure from his WV base to vote for Kavanaugh.