Biden and his (admittedly tiny cadre of) strong supporters aren't moving left. Half of them barely use the internet, and the other half are so entrenched in their own class interests that you might as well try to convince the Tsar to cut his own head off. Use your energy to organize and educate the undecided and apathetic, because they're going to radicalize one way or the other and we'd much rather they decide "everyone deserves dignity" than "brown people are subhuman."