In my opinion, the best case scenario is that the GOP dies (it happened with the Whigs!) and a new, more progressive party (maybe DemSoc) becomes relevant to the left of the Democrats. The Dems become the new Conservatives (since they basically are anyway) and the left wing becomes the moderate left. The overperformance of Abughazeleh (even though she didn’t win) and the shocking effectiveness of Mamdani now that he’s in office make this slightly less impossible than it would’ve seemed even a year ago.