An interesting observation from The Intercept: in terms of union nominations, Hillary Clinton wins the union's nomination whenever the leadership of the union decides whom to nominate. If the membership decides, the endorsement goes to Sanders.
I have noticed that seems to apply to left-wing political action organizations like MoveON, too. They set a high bar for endorsement, saying that they'd only endorse a candidate if a three-quarters supermajority sided one of the candidates. Sanders won. Likewise with Howard Dean's PAC, which put the matter to a vote and got a vast supermajority for Sanders.
Even members of the old Clinton administration are starting to break away: yesterday, Robert Reich endorsed Sanders.
For now, before anybody has voted (and before the FBI has made its impact known), Clinton has a narrowing national lead. She's hoping that superdelegates, union leaders, and other power players will pull everyone into line.