The Andrew Gillum campaign says it has sent a cease-and-desist letter to television stations running a Republican Party of Florida commercial that labels the Democratic gubernatorial candidate "corrupt" and attempts to directly tie him to an ongoing FBI investigation.

Calling the ad "demonstrably false," attorney Glenn Burhans Jr., penned a letter Thursday saying that the campaign "will take all available resources to prevent the spread of the false and defamatory advertisement." Burhans wrote that the attack ad badly exaggerates and misstates the articles cited as source material for statements claiming the mayor is under investigation, took "illegal trips" to New York and Costa Rica with lobbyists and "refuses to disclose who's paid him.""In short, the advertisement constitutes libel and slander of the worst sort," Burhans wrote.

Meredith Beatrice, a spokeswoman for the Republican Party of Florida, said "we stand by the ad."

The commercial in question began running Wednesday across the state. Burhans said that while it was funded by the RPOF, it was approved by GOP nominee Ron DeSantis, among other party figures.

The ad says Gillum, the mayor of Tallahassee, is "running from the FBI" and also includes the text "Andrew Gillum FBI Investigation." It cites reports over the past year that documented the exploits of federal investigators who posed undercover as businessmen interested in doing business in the city.

Subpoenas sent to the city in 2017 and uncovered by the Tallahassee Democrat show the investigation has focused on the city's Community Redevelopment Agency and on several entrepreneurs and lobbyists, one of whom is a college friend of Gillum and former mayoral campaign treasurer. But Gillum, who met with the FBI around the time that news of the investigation broke last year, has long said he was told he is not a subject of the investigation.

To date, there has been no public information or reports to contradict that statement, and no charges have been filed.

Gillum's campaign also argues that the ad crosses the line by using the words "possibly illegal" and "illegal" to describe much-scrutinized trips that the mayor took to Costa Rica with Tallahassee lobbyists with whom the mayor is friendly, and to New York with businessmen who turned out to be undercover FBI agents. The commercial uses a picture published by the media that shows Gillum on a boat in New York with lobbyist and former volunteer campaign treasurer Adam Corey, who was among the individuals named in federal subpoenas sent to the city.

The ad cites a Tallahassee Democrat article as the basis for the "possibly illegal" trips claim, but the article discusses an ethics investigation, not the FBI probe, Burhans writes. Finally, Burhans objects to a statement in the ad that alleges that Gillum refuses to say who's paid him, arguing that it misstates a POLITICO Florida article that detailed a list of receipts and bank statements Gillum released to the media shortly after his primary election win.

Beatrice said Wednesday that the RPOF was pulling the commercial in areas hit by Hurricane Michael. But Gillum wants them pulled down everywhere.

"The advertisement is emblematic of the corrosive and divisive rhetoric tearing our society apart," Burhans wrote. "And the fact that it is being run in the midst of a devastating hurricane is reprehensible."