The early voting state is the first 2008 Democratic contest with a large African-American electorate -- more than half of the primary voters are expected to be black -- and could provide vital clues about the outcome of the national race.

Black voters could make a difference in Democratic primaries in Florida, scheduled to vote on the same day as South Carolina, and many of the more than 20 states that vote the next week -- including big states like New York, New Jersey and Illinois that could decide the nomination.

"The Democrats all know they need the African-American vote to win," said James Johnson, a pastor at a nondenominational Charleston church who works with the city's poor residents. "The question is what are they going to do about it? We're listening."

Obama, an Illinois senator who would be the first black president, launched his first ad aimed at black radio audiences on Tuesday. Along with Clinton and former North Carolina Sen. John Edwards, who won the state's 2004 primary, he plans a full-court press to woo the state's blacks.

Obama must win over black voters who are more familiar and comfortable with Clinton, a New York senator and former first lady with high appeal among black women. Her husband, former President Bill Clinton, remains extremely popular with black voters.

A CNN poll in South Carolina last week found Clinton with a double-digit lead on Obama statewide and among black voters. A different pollster last month found Obama leading statewide and with blacks. Edwards, a South Carolina native, ran a distant third in the state polls.

The state polls mirror national polls showing Clinton, Obama and Edwards running 1-2-3 in a crowded Democratic field of candidates for the November 2008 election. - DDNEWS India