Last time around, the black vote took an insurgent left-wing candidacy and helped destroy Hillary Clinton's chances at the White House. The far left is hoping Bernie Sanders is Barack Obama.
But this time around, the black vote is Hillary Clinton's firewall. Bernie Sanders is about as popular with black voters as slavery. Despite the Killer Mike theater, that's never going to be his base. It's why Hillary Clinton effectively used #BlackLivesMatter to destabilize his campaign.
It's also why there are hard limits to how well Bernie Sanders can do against Hillary in states where the Democratic base is a lot less white than New Hampshire.
Bill Clinton is still popular with black voters and with no Obama endorsement, Hillary Clinton boasts more White House ties than Bernie Sanders does. Barring Biden going in and campaigning, and he still seems to be hoping for an FBI indictment that will let him swoop in and take over the race, for Bernie Sanders, that gives Hillary Clinton clear, core minority vote advantages.
Hillary Clinton's awkward lurch to the left is alienating the white working class voters she needs to beat Bernie Sanders. They're the type of people who want a moderate Democrat. Not another politically correct nutjob rambling about white privilege, as Clinton awkwardly did. But she needs to retain enough moderate Democrats and black voters to hold off the Bernites. That's a difficult trick in New Hampshire, but a lot easier in South Carolina.
Ironically it's the very "diversity" that the left cites which has made it so difficult for it to win. Diversity cuts ways. Most minority voters are basically conservative. Obama hijacked the election using race. And the left's Obama this time around is a rambling old white Socialist with a thick accent who has zero appeal to minority voters.