Josh Marshall captures something that has really been bugging me about the rhetoric coming out of the Sanders camp:

The Sanders campaign often talks as though it’s only talking about an establishment of insiders and power brokers. But that just leaves millions of activists and voters erased from the picture entirely. The last 72 hours is a case in point. To hear many Sanders surrogates describe it, the establishment and power brokers closed ranks and pushed Biden into the lead. But again, this just pretends like millions of voters don’t exist, or function as pawns of party elites. So you have one theory of political agency for Sanders supporters and another for everyone else. This stands no kind of political scrutiny.

Did key endorsements, especially from Jim Clyburn but also from Klobuchar, Buttigieg and O’Rourke, have an effect? Of course. But focusing only on those ignores what was a parallel reaction among numerous ordinary Democratic voters to the events of the last ten days. The interplay between these two developments is key.

Here we get to a critical, distinct dynamic of this race. Sanders was dominating the primary race with about 25% support. If you won’t or can’t expand your coalition beyond that number you’re in a highly vulnerable position, particularly if you’ve created a confrontational or antipathetic relationship with other factions within the party.