A racial issue in the Democratic contest
Here's the thing, though. Of all the states that have voted so far, Hillary has won Alabama, Arkansas, Georgia, Iowa, Massachusetts, Nevada, South Carolina, Tennessee, Texas, and Virginia. Bernie has won Colorado, Minnesota, New Hampshire, Oklahoma, and Vermont, and came very close in Iowa and Massachusetts.
Notice the pattern. Bernie does well only in states with an overwhelmingly white population. Hillary has swept every Southern state that has voted so far. Most Southern states have large black populations, as does Texas (Texas and Georgia also have large numbers of Latinos) -- and in those states, those minority populations form the core of the Democratic party. Starting with South Carolina, they've voted overwhelmingly for Hillary.
For a discussion of why black voters favor Hillary so strongly, see this post at Horizons -- it has also been observed that Bernie's tendency to view all issues through the lens of economic inequality does not play well with those who demand recognition of racism as a separate problem existing beyond economic issues. (And "Bernie-splaining" to black voters is not going to work.)
The US population is 13% black and 17% Latino. Within the Democratic party, the percentages are obviously even higher, since few members of those groups identify as Republican. The fact that Bernie has been unable to win much support among them suggests that he would have great difficulty unifying the party if he were to be the nominee. Beyond that, it is actually necessary and appropriate that the party's choice of nominee should be ratified by the black and Latino voters without whom the party has no hope of winning on a national level. We can't have a nominee chosen with only, or nearly only, white support. We need a candidate who can fully engage the support of all of the Democratic base in order to be sure of beating Trump, or whomever the Republicans nominate, in November.
Something to consider, when your state's primary arrives.