They're in an awful catch-22. He promised a black woman (his first mistake, narrowing the pool so severely right out the gate like that), and at the moment the black vote is, well, volatile. The options who agree with the party insiders on most platform issues all have records as cops or prosecutors that resonate poorly with the current demands for reform, and they cannot risk depressing the black vote this year by putting forward the Old Guard on that issue. But the ones who appeal to the protesters all are saying radical nonsense about abolishing police departments that'll turn off the moderate majority they need to sway to their side in November.
Plus there's the rarely discussed feud currently happening over the official party platform, because Bernie winning CA means he has enough delegates that they need him to publish their agenda for the election. All sorts of intra-party civil wars are happening over not being far left enough on immigration, healthcare, and education reform. Which, again, poses an obstacle to getting the moderate vote.
He's the guy Hillary finally paid back for volunteering to step down as head of the DNC ~6 months after the party got trounced in 2010, nominating her campaign manager to replace him so the non-Clintonite purges could begin.
