Your post is the standard bit of gaslighting- it refuses to acknowledge that the polls showed Sanders running just as strongly as Biden in the firewall and Warren running competitively there as well. It's really getting tiresome that the party establishment types keep acting as if the polls showed Biden ten points ahead of Trump but had Bernie and Warren twenty points behind or something.

The hardline "only a centrist can win" canard was never justified by the actual polls, and it's time to give it a rest, now that Bernie's never going to be president.