According to MSNBC's exit polls, Obama won by something like 30 points.
Age was also important. 49 percent of folks under 30 years of age voted for him. He and Edwards did well among college-educated adults.
Obama did horrible among whites who are not college-educated.
Update: More from Time and CNN.
Per the network/AP early exit poll results:
African-Americans: Obama 81%, Clinton 17%, Edwards 1%
African-American women: Obama 82%, Clinton 17%, Edwards 0%
Whites: Edwards 39%, Clinton 36%, Obama 24%
Edwards winning white men, Clinton white women.
Economy clear top issue.
ABC News: Preliminary exit poll results indicate … a “very large turnout” among African-American voters — definitely more than 50 percent of voters in South Carolina are black, according to the early numbers, compared to 47 percent in 2004, and 43 percent in 1992.Read more here
ABC polling director Gary Langer: “Women and African-Americans… are turning out in large numbers today. Preliminary exit poll results indicate that just over half are blacks this year; if that holds in final data later tonight, it would be the highest turnout among African-Americans in any Democratic presidential primary at least since 1984.”