Broad appeal among democrats, but the candidate with the best chances in the national election is not the center Democrat, it's the center American, which if you imagine Democrats and Republicans being two ranges butted up against the center, is the rightmost Democrat!

I don't believe republicans or "independent" voters will ever actually cross the aisle anymore. Trump still has massive MASSIVE support from registered republicans.

Less than a third of Americans identify as republican.

And that third gives Trump something like a 90% approval rating. My base assumption is that in order to win them over, you'd have to significantly match up with their world view. A significant part of their world view seems to be that "Democrat = bad" so that's kind of a non-starter, and I'm not sure I'd want someone elected who has compromised their platform, morals, principles, etc enough to be liked by people who still support Trump.

Bernie Sanders is the most popular candidate among all Americans. Republicans are going to vote for Trump no matter what and a center-right Democrat will not change this. The only way to defeat Trump is to produce a record turnout among young people and people that have felt abandoned by the political establishment that would otherwise not vote. The only candidate that can possibly do this is Bernie Sanders.

That’s not what the head-to-head matchups against Trump say. Polls have shown over and over again that almost any democrat beats Trump in a head-to-head matchup, but that Bernie, Biden, and Bloomberg are all just about tied in beating Trump by the largest margins.

Most voters don’t have a coherent ideology. The ever-appealing “center” is not a real thing; it exists only wherever voters can be convinced it exists.