COLUMBIA, S.C. - Barack Obama routed Hillary Rodham Clinton in the racially-charged South Carolina primary Saturday night, regaining campaign momentum in the prelude to a Feb. 5 coast-to-coast competition for more than 1,600 Democratic National Convention delegates. Former Sen. John Edwards of North Carolina was running third, a sharp setback in the state where he was born and scored a primary victory in his first presidential campaign four years ago. The Associated Press made its call based on surveys of voters as they left the polls. About half the voters were black, according to polling place interviews, and four out...