As tensions mount between Hillary Clinton and Barack Obama, the two leading Democratic candidates for president, the air has grown thick with allegations and counter-allegations that they and their surrogates have encouraged ungrounded personal attacks with racial undertones. Some have an unsavoury echo of "dog-whistle politics", when a candidate or a supporter makes a remark that has an impact on a section of the voting public but goes unnoticed by most voters.
New York's attorney general, Andrew Cuomo, a prominent Clinton supporter, suggested Mr Obama was trying to "shuck and jive" (in other words lie), his way to the White House. Then Congressman Jesse Jackson Jnr, an Obama supporter, questioned how tears could well up in Mrs Clinton's eyes for New Hampshire but not for the black victims of Hurricane Katrina.
As the pair head towards the 26 January South Carolina primary, where African Americans are a key constituency, Mrs Clinton is trying to control the damage caused by her own clunky remarks about the civil rights hero Dr Martin Luther King. She was accused of playing down Dr King's importance to the civil rights movement when she said his "dream began to be realised when President Lyndon Johnson passed the Civil Rights Act of 1964. It took a president to get it done".
Yesterday, Mrs Clinton was in New York honouring Dr King's birthday. "This is an unfortunate storyline that the Obama campaign has pushed very successfully," she said, accusing her opponent's campaign of fanning the flames of a racially charged dispute. A Clinton aide said the Obama campaign had leaked quotes by Mrs Clinton and her allies that seemed racially insensitive. Mr Obama, who has tried to dodge the bubbling debate over race, called her remarks "unfortunate" and "ill-advised".
The Clinton campaign also had to explain away remarks about Mr Obama's youthful experiments with cocaine by the warm-up act for one of her South Carolina speeches.
Bob Johnson, founder of TV's Black Entertainment Network, said the Clintons were "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". The Clinton campaign said he was referring to Mr Obama's time as a community organiser.