Well a little history lesson - in 1992 Jerry Brown refused to endorse Bill Clinton and his dead enders booed at the convention too. Don't forget the Democratic party has always had its crackpots, the Sarandon contingent who would rather vote for Hugo Chavez (and I am dead serious and there are pics to prove it) than nearly any Democrat. I do believe they are mentally ill, but they are also extremely privileged, they are white, nearly every single one of them is white, able bodied, and so inoculated from the worst of a Trump presidency.
And here is the thing okay? They never vote Democrat. The idea that these 3rd party fanatics that Bernie brought into our tent and allowed to piss inside of it instead of pissing in from outside of it, are going to affect the outcome is ludicrous because none of them ever voted Dem in the first place. Why should Susan Sarandon be at the Democratic convention? She's not a democrat, when has she ever voted Democrat? She won't vote for Hillary, she didn't vote for Obama, she didn't vote for Gore. What is her ass doing inside my tent? See that is what I would like to know.
The lauded Millennials will vote for Hillary. The dead enders are the old Chavez crew for the most part. Sure they'll pick up a few newbies, but that won't make a difference. 90 percent of Bernie voters are already telling pollsters they will vote for Hillary. That's the story. But it's not one you'll hear much about.