A Biden nomination could very likely mean 4 more years of Trump. Biden is one of those weak, establishment candidates, and hopefully his numbers continue to drop, like they have been. Currently if you add the support for Warren and Sanders their polling numbers are higher than Creepy Joe. Both Warren and Sanders refuse to accept corporate donations, both of them have strong policies and seem very sincere regarding the threat of climate change. Is it too early for them to join forces? Maybe. I don't think Biden holds a chance of winning the presidency, but a Warren/Sanders ticket seems pretty good. Maybe they could bring Yang's Universal Basic Income policy to the table, and get even more votes. No matter what, we have to be sure to not repeat the mistakes that lead to Trump being put in office. I think that both means that for the final vote, progressives should vote for whatever Democrat is left standing, but also that whatever Democrat is standing should not concede, and also that we should stop Biden in his tracks because he is not the right person to win.