Here’s a more accurate assessment of the situation: The Berners are going to walk in any scenario where the party does not bend the knee to him.

If he fails to win a plurality of delegates, they’ll declare the DNC “rigged” the process and walk.

If he wins a plurality but fails to meet the threshold to win on the first ballot, then loses on the second, then they’ll scream it was “rigged” (again) walk away.

If there’s a brokered convention that leads to anything but a Bernie nomination, then they’ll walk.

So to say we can’t win without the Berners is to say that the rules be damned, Bernie must be the nominee if we want to win.