In S.C., a cauldron of history, politics, and race

The Confederate flag flies above participants in a celebration today of the Rev. Dr. Martin Luther King Jr. at the South Carolina state capitol.

COLUMBIA, S.C. -- Past, present, and future collided today as the leading Democratic presidential candidates joined South Carolinians to observe the birthday of the Rev. Dr. Martin Luther King Jr. at the state capitol here.

The past: this state's checkered history of race relations, evidenced by the angry denunciations of the Confederate flag that still flies on the capitol lawn, and by the flag's defenders who formed a small protest across the street.

The present: a hard-fought contest among Barack Obama, Hillary Clinton, and John Edwards for top prize in this Saturday's Democratic primary, in which black voters, expected to make up more than half the electorate, will be key.

The future: the progress paving the way for a woman and an African-American to have the best shot ever at winning the presidency.

Leaders of the National Association for the Advancement of Colored People led the King celebration, urging participants to both recognize how far the country had come but continue fighting for justice. They urged the audience to vote.

"The same hands that picked cotton will have the opportunity to pick the next president of the United States," said Lonnie Randolph, president of the South Carolina branch of the NAACP. "We have power beyond measure. Let's put that power to work."

The three candidates all gave brief remarks, gently infusing their campaign messages into tributes to King and his legacy, which have been the subject of controversy in recent weeks after Clinton was accused of downplaying King's civil rights successes. Today she made certain to praise him, saying, "He led a movement of works, a movement of people across our country who raised their voices, rolled up their sleeves, and worked for justice."