By ADAM NOSSITER and JANNY SCOTT NEW ORLEANS - The sharp surge in black turnout that Senator Barack Obama has helped to generate in recent primaries and Congressional races could signal a threat this fall to the longtime Republican dominance of the South, according to politicians and voting experts.
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. In West Virginia, where more than three-fourths of white voters chose Mrs. Clinton, 20 percent of the white voters said the race of the candidate mattered in their choice.