COLUMBIA, S.C. - The Rev. Al Sharpton all but admits he has no shot of winning the Democratic nomination for president, but that doesn't deter the thousands who have leapt to their feet and danced on chairs in recent days to cheer his fiery words as he preaches to campaign rallies across South Carolina. Just last week, after a vintage Sharpton speech full of sharp humor and wisecracks designed to paint his fellow Democrats as weak on issues of race and poverty, dozens of students at a historically black college near the capital heeded his call for campaign volunteers by...