The FBI arrested four people in New Orleans on Monday after discovering a plot to wiretap Sen. Mary Landrieu's (D-La.) office phones, according to media reports. Among those being held is James O'Keefe (pictured here), a conservative filmmaker best known for posing as a pimp in undercover videos of ACORN field offices.

FBI Special Agent Steven Rayes alleges that O'Keefe aided and abetted Joseph Basel and Robert Flanagan, who dressed up as employees of a telephone company and attempted to interfere with the office's telephone system. Flanagan is the son of William J. Flanagan, acting U.S. attorney for the Western District of Louisiana, a Democratic official said.

A witness from Landrieu's staff told the New Orleans Times-Picayune that O'Keefe was present in the office and claimed to be "waiting for someone to arrive."

The fourth suspect, Stan Dai, was accused of aiding and abetting Basel and Flanagan. All four were charged with entering federal property under false pretenses with the intent of committing a felony.

Citing an "ongoing investigation," Landrieu's office declined to comment.

Meanwhile, conservative bloggers reacted with dismay Tuesday.

"This is neither a time to joke nor a time to recklessly accuse Democrats/liberals of setting this up," Michelle Malkin wrote. "Let it be a lesson to aspiring young conservatives interested in investigative journalism: Know your limits. Know the law. Don't get carried away. And don't become what you are targeting."

Updated at 4:37 p.m.