Brandishing a copy of the leaflet, Clinton said the Obama campaign was spreading "false, misleading, discredited information" about her health-care plan.

"Senator Obama knows it is not true that my plan forces people to buy insurance even if they can't afford it," Clinton said. "It is blatantly false and yet he continues to spend millions of dollars perpetuating falsehoods. It is not hopeful. It is destructive, particularly for a Democrat to be discrediting universal health care."

Obama said the content of the leaflet was correct. He said he was puzzled by the sudden "change in tone" by his rival because the leaflets Clinton referred to were sent out days or weeks ago. He suggested there was something "tactical" about her attacks now.

"The notion that somehow we're engaging in nefarious tactics I think is pretty hard to swallow," he told reporters. "There's nothing in there that's factually inaccurate."

March 4 Contests

Clinton, a New York senator and former first lady, would be the first woman US president if she won the general election, and Obama, an Illinois senator, would be the first black president.