Old Polarities Persist in Dem Race

In Ohio, 18 percent of white voters said race was important to their vote. Among them, 76 percent backed Clinton. She won by 16 points among women in Ohio and 29 points among whites.

In all, Clinton is winning the majority of white votes in Democratic primaries in which both candidates competed.

Obama has performed best among whites in liberal Vermont and his home state of Illinois, although he has also edged Clinton in the white vote in Wisconsin, Virginia, Utah and New Mexico.

All told, voter surveys suggest that Clinton ends up with more votes because she's a woman than Obama nets because he's black.