Obama Carries South Carolina by Wide Margin

But

More than half of the Democratic voters were African-American, and surveys of voters leaving the polls suggested that their heavy turnout helped propel Mr. Obama to victory.

Mr. Obama, who built an extensive grass-roots network across the state over the last year, received the support of about 80 percent of black voters, the exit polls showed. He also received about one-quarter of the white vote, with Mrs. Clinton and Mr. Edwards splitting the remainder.

In particular, Mr. Obama was helped by strong support from black women, who made up 35 percent of the voters. Mrs. Clinton, with the help of her husband, had competed vigorously for black women voters, but Mr. Obama received about 80 percent of their support, according to the exit polls, conducted by Edison/Mitofsky for the National Election Pool of television networks and The Associated Press.