Mayor Willie Herenton stepped before television cameras to announce he had made a startling discovery: Rich, white businessmen were plotting to derail his re-election by videotaping him having sex with a strip club waitress.

The revelation earlier this month added a racial dimension to Herenton's campaign for a fifth term that would make him the longest-serving mayor in Memphis history.

Herenton, the city's first elected black mayor, stared into the cameras, and issued a warning for the "snakes" conspiring against him.

"One snake who's been crawling in the grass finally raised his head," the mayor said at a June 14 news conference. "But I want you to know that there's another snake in our midst ... and I'm going to put him on notice.

"When he raises his head ...," Herenton said, pausing with a slow smile. "You complete the rest of it."

It was an edgy performance, even for Herenton, a 6-foot-6 former boxer with a taste for political combat and a self-assuredness that drives his critics to distraction. He offered no evidence and refused to name the "wealthy business leaders" he said were behind the plot.

"He's always been very aggressive, but in this case, it did look like he was grasping for a reason to be a victim," said Larry Moore, a University of Memphis professor and political consultant.

The conspiracy claims came from Gwendolyn D. Smith, a 29-year-old former waitress who said she was offered $150,000 to seduce the 67-year-old mayor and videotape their sexual encounter.

Smith, who is also black, made the allegations in a letter to the state prosecutor in Memphis. She said her former lawyer, Richard Fields, recruited her for the plot and promised she would be paid by unnamed "benefactors." She also accused Fields of sexually assaulting her.

Fields, who is white, is a well-known civil-rights lawyer in Memphis. He was once married to Smith's cousin and represented Smith in 2004 when she pleaded guilty to felony charges of forgery.

He denied Smith's allegations and described her as a con artist and drug abuser. "She's desperate for money," he said. "She thinks the mayor or somebody will pay her money."

A few days after Herenton's news conference, Smith was back in jail in Nashville for failing a drug test while on probation.

"It's a strange story," said political scientist Marcus Pohlmann of Rhodes College of Memphis. "It's almost too strange to be taken seriously unless there's a paper trail, and maybe there is."

A recent poll in The Commercial Appeal newspaper found 60 percent of respondents were opposed re-electing the mayor in October, with his popularity slipping among black as well as white voters.

But if the mayor were seen as a victim of a white conspiracy, his black voting base could be re-energized, Moore said.

"In many ways what the mayor was doing is basically just smart, hardball Memphis politics," Moore said.

Herenton said Smith's claim bolstered his belief that conspirators were plotting to undermine his bid for re-election "by any means necessary."

A special state prosecutor has been appointed to look into Smith's allegations, and the Memphis police are investigating, too.

Herenton also has asked the Justice Department to look into Smith's claim, since she contends an FBI agent may have been in on the plot, an allegation the FBI denied in a statement. Herenton did not say why the FBI would conspire against him.

Herenton, who was also the city's first black school superintendent, came to the mayor's office by beating a popular incumbent by just 142 votes in 1991. It was the first mayor's race in which black registered voters outnumbered whites, and it was the closest in the city's history.

Since then, Herenton has overseen a major revitalization of downtown Memphis, helped bring an NBA franchise to town and kept the city on a sound financial footing.

The city of 650,000 is now 60 percent black, and Herenton has had little trouble with re-election, drawing support across racial lines.

But critics argue he has been mayor too long, pointing to his frequent clashes with the City Council, which he describes as incompetent, and his oft-repeated statements that God wants him in the mayor's office.

Herenton, who is divorced, makes no secret about having an active social life and publicly acknowledged two years ago that he had fathered a child with a 31-year-old woman he was dating.

That disclosure and Herenton's quick acceptance of paternity seemed to cause him little trouble politically, said Pohlmann, and he likely would be a hard target to hurt with a sex scandal.

"He's a single guy. He goes out with women. Not much of a story there," Pohlmann said.

Herman Morris, a longtime Memphis lawyer and former president of the city utility, is expected to be one of Herenton's strongest challengers and one of the few serious black opponents the mayor has had since taking office.

John Ryder, a co-manager of Morris' campaign, said many voters will likely ignore Herenton's conspiracy claims.

"The underlying allegations are pretty bizarre," Ryder said. "And his reaction was pretty bizarre."