UPDATED 01/31/11 5:30 p.m.

CHICAGO (CBS) – A fiery exchange occurred Sunday between mayoral candidates Carol Moseley Braun and Patricia Van Pelt-Watkins, as allegations of drug use dominated a candidates forum.

When Watkins questioned where Braun had been for 20 years, the latter candidate fired back by saying Watkins had been using crack-cocaine.

“Patricia, the reason you didn’t know where I was for the last 20 years is because you were strung out on crack,” Braun, staring at Watkins, said at Trinity United Church of Christ on the South Side. “Now, you have admitted to that.”

Watkins denied the charge before forum organizers cut her short. The community activist has admitted past drug use but says she has been sober for 25 years. She says she has never even seen crack.

“I believe I’m due an apology but I don’t expect one to come,” Watkins said at a news conference Monday. “I should be able to ask any person who’s running for office where you been, and I should not be called a crack addict because I said that.”

Braun, a former U.S. senator and ambassador, offered no apologies.

Their respective supporters also clashed Sunday. Watkins backers staged a noisy demonstration at a West Side church where Braun appeared. Braun’s people were there, too, in a counter-demonstration.

A spokeswoman for Watkins said the group of supporters included some black leaders who say they were wrongly identified in Braun campaign literature as endorsers of Braun. The Braun camp denied that.

Braun spokeswoman Renee Ferguson said Watkins was acting as a “spoiler and really, really, really desperate.”

Also attending the forum where the explosive remarks were made Sunday were mayoral candidates Gery Chico and Miguel del Valle.

Frontrunner Emanuel was not present for the debate. He declined to weigh in on Braun’s outburst. When asked about it Monday, Mayor Daley would only say that everyone knows someone who has struggled with drug or alcohol abuse.

The mayoral election is Feb. 22. Early voting is now in progress.