US:Race has moved to the centre of the Democratic presidential contest as Hillary Clinton and Barack Obama exchanged sharp accusations ahead of next week's primary in South Carolina, where African Americans could make up half the electorate.
Mrs Clinton has accused the Obama campaign of distorting statements she and her husband, former president Bill Clinton, made last week, which some black commentators have condemned as racially insensitive.
A new poll shows Democratic voters dividing along racial lines, with Mrs Clinton leading Mr Obama among white voters by 41 per cent to 27 per cent, while black voters back Mr Obama over Mrs Clinton by 66 per cent to 16 per cent.
Mrs Clinton came under fire for suggesting that Martin Luther King's dream of racial equality was not realised until Lyndon B Johnson signed the Civil Rights Act into law. Mr Clinton has been criticised for dismissing as a "fairy tale" Mr Obama's account of his record on the Iraq war.
Mrs Clinton has accused the Obama campaign of fuelling the controversy, insisting that she had not sought to downplay Dr King's pre-eminent role in the civil rights movement but only to point out that the civil rights leader needed political allies to make his dream a reality.
"I think it offended some folks who felt that somehow diminished King's role in bringing about the Civil Rights Act," Mr Obama said.
"She is free to explain that, but the notion that somehow this is our doing is ludicrous."
Mrs Clinton had more explaining to do after Bob Johnson, the billionaire owner of Black Entertainment Television, appeared to refer to Mr Obama's youthful drug use when he introduced the former first lady at an event. "To me, as an African American, I am frankly insulted the Obama campaign would imply that we are so stupid that we would think Hillary and Bill Clinton, who have been deeply and emotionally involved in black issues - when Barack Obama was doing something in the neighbourhood; I won't say what he was doing, but he said it in his book - when they have been involved," Mr Johnson said.
Mr Johnson later said in a statement released by the Clinton campaign that his comments referred to Mr Obama's work as a community organiser in Chicago "and nothing else. Any other suggestion is simply irresponsible and incorrect."
