There isn't really a discussion here. Sanders got crushed. He is basically performing like Romney v Obama within each racial group. That wasn't enough to win in a general election electorate and it's sure as hell won't cut it in a Democratic primary.
‘But I know this black guy who DJ’s sometimes in a bar in Dumbo and he’s definitely voting for Sanders...’
Let’s be honest, Sanders is a liberal Trump.
Evidently Sanders is 100 times the man Trump is, but a shift in the electorate allowing for an increasing bloc of ‘millennial’ voters, the rise of the religious ‘nones’ to becoming an actual voting bloc on par with the voting power evangelical right (which is so far taking a beating) and the rise of the ‘angry’ white liberal who chastises the party for not being liberal enough is essentially a ‘reactionary left’ mirror to the ‘reactionary right’ of the GOP.
They are politically opposite and personally one is far more welcome than the other but in terms of potential alienation from their respective parties, dismissal and mistrust of the party machinery, or of the centre ground and the inability to connect with voters outside of their bubble
and be exasperated at why these people don’t connect with them and some of the ‘media against us’ conspiratorial hot air, they are functionally the same.
There is a undercurrent that in some outlets has even become exposed to the surface (like the cesspit Daily Kos has become), that blacks and latinos ‘don’t know what’s good for them’ and if they did would vote for Bernie. ‘Whitesplaining’, even with good intentions is cringe-worthy and least and at most, insulting.
Sanders has a problem. It is very real. It won’t go away by making vague appeals to GE matchup polls or back of the envelope calculations that he might have won ‘minority’ voters in Vermont. He has a problem with non-whites, non-liberals, women and the over 45’s. The Democrats need to win the election with the same coalition that swept Obama to power. Even if black turnout drops the continued drift of latino voters by default to the Democrats should keep things on par.
If anything we are seeing a reversal of the 2008 primary; Clinton is continuity Obama and carries his coalition (except the youth). Sanders appeal is becoming limited to white voters like Clinton in 2008, except they are young and angry and not old and bitter.