This is really depressing: Sanders claiming that there will be a contested convention, and suggesting that the nomination fight was rigged. Can someone tell Bernie that he’s in the process of blowing his own chance for a positive legacy?

Here’s how the narrative could have run: although he fell short of actually getting the nomination, Sanders did far better than expected, giving him and his movement a good claim to have a big say in the Democratic agenda for 2016 and perhaps setting the movement up as the party’s future. But to take that position — to turn defeat in the primary into a moral victory — he would have had to accept the will of the voters with grace.

What we’re getting instead is an epic descent into whining. He dismissed Clinton victories driven by black voters as products of the conservative Deep South; he suggested that his defeat in New York was unfair because it was a closed primary (you can argue this case either way, but requiring that you identify as a Democrat to choose the Democratic nominee is hardly voter suppression — arguably caucuses are much further from a democratic process); then, with the big loss in the mid-Atlantic primaries,he has turned to a sort of fact-free complaint that any process under which Bernie Sanders loses is ipso facto unfair, and superdelegates should choose him despite a 3 million vote deficit.

At this point it’s as if Sanders is determined to validate everything liberal skeptics have been saying all along about his unwillingness to face reality — and all of it for, maybe, a few weeks of additional fundraising, at the expense of any future credibility and goodwill. Isn’t there anyone who can tell him to stop before it’s too late?