Hot off the presses. Final S-USA poll of NC:
SurveyUSA Election Poll #13844 Black Voters (32% of the electorate)
Clinton 12%
Obama 85%
White Voters (64% of the electorate)
Clinton 62%
Obama 32%
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Conservative Voters (18% of the electorate)
Clinton 49%
Obama 40%
Moderate Voters (40% of the electorate)
Clinton 52%
Obama 44%
Liberal Voters (19% of the electorate)
Clinton 41%
Obama 57%
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It's all racial bloc voting. The demographic numbers make it impossible for Clinton (or any white candidate) to win the NC Democratic Primary against a African American opponent. Those same numbers make it impossible for a Democratic African American nominee to win the state in November.
It's hard to paint a more vivid polling picture of the coalition the Dems will likely take to the November election: African Americans & extreme liberals.