They won't try lol. The Harris campaign made it quite clear that it wasn't part of their platform. The Clinton campaign argued against it. The Biden campaign said something about a public option that wasn't mentioned again after the election. The Dems did their best to stop any momentum Sanders had when he campaigned on single-payer.
They don't want to do it.
Ah, yes, so we've gone from insisting that Dems support something they will openly tell you they oppose, to pure scolding. This didn't work a month or so ago, I don't know why you'd expect it to work now. I'd love to support Dems. They need to make it a worthwhile effort.