Here's the thing.
I've always sort of assumed that the primaries were largely a show, basically drumming up the illusion that all of the candidates could be "the one" in order to draw money in from everyone who supports them. That's why I've always rolled my eyes when people freak out and start shouting conspiracies when whatever dark horse candidate the internet falls in love with doesn't get the nomination.
I'd put folding money in the pot right now that the real movers and shakers of the DNC are already like 80-90% sure who their candidate is gonna be and have a very, very small handful (no more than 2 or 3) even on the broader "might possibly be it" list.