It’s not that Sanders is running a weak campaign. But he is, in a way, running the wrong campaign. He’s the frontrunner for the Democratic nomination — at least he was until tonight — but he’s still running as an insurgent. The political revolution was supposed to close the gap between these realities: If Sanders could turn out enough new voters, he could sweep away the Democratic establishment and build his own party in its place. But going all the way back to Iowa, that strategy failed. Sanders won as a Democrat, not a revolutionary, and he needed to pivot to a strategy that would unite the existing Democratic Party around him.
But it’s hard to move from treating the Democratic Party establishment with contempt to treating it like a constituency, and so far, the Sanders campaign hasn’t.