Obama leads in South Carolina; McCain up in Florida: poll

By John Whitesides, Political Correspondent

COLUMBIA, South Carolina (Reuters) - Barack Obama expanded his lead on rival Hillary Clinton to 15 points heading into South Carolina's bitterly contested presidential primary, according to a Reuters/C-SPAN/Zogby poll released on Saturday.

Obama, an Illinois senator, gained two points on Clinton overnight to lead 41 percent to 26 percent just hours before voting began in Saturday's primary. John Edwards was in third place after slipping two points to 19 percent.

In Florida, where Republican presidential contenders meet in a critical primary on Tuesday, John McCain had a narrow 3-point advantage on rival Mitt Romney, 31 percent to 28 percent, in the state's initial rolling poll.

The polls in both states had a margin of error of 3.4 percentage points.

Obama has led Clinton by double-digits in all four days of polls in South Carolina, fueled by a huge advantage among the black voters who are expected to make up about half of the electorate in the first Democratic primary in the South.

Obama, who would be the first black U.S. president, was favored by 62 percent of black voters, with Clinton at 18 percent and Edwards at 5 percent.

Edwards, a former North Carolina senator who won the state during his failed 2004 White House run, and Clinton, a New York senator, were tied among white voters at 35 percent each. Obama was at 19 percent.

"Obama holds solid leads in every section of the state, and among both men and women," pollster John Zogby said.