So John James got 46% of the vote in Michigan even after being outspent 2:1. And none of the folks voting for him had the lighter shade of melanin in their skin?
And he did so by winning in the areas where the majority of voters are white. He lost to a white woman in Detroit, Flint, and other areas where the majority of voters are African American.
Of course it is possible African American voters did not like his choice of a wife, or they really are so dedicated to the policies of the Democratic party that they would not consider voting for him.
But Bernie's theory is refuted by the data in Michigan.