I actually think there's more tolerance for big Keynesian spending in the Democratic party than people would care to admit.
But first assume zero Republican votes (despite what Biden says, I don't think he's going to charm them into working with him and I suspect Josh Hawley might not actually be a leftist). Even if you nuke the filibuster or abuse the hell out of reconciliation you need to get to 50 votes and I don't anticipate the Dems winning the Senate with much, if any, cushion. Shit gets very difficult when you need to hold together your entire caucus.