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, 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.

Landrieu said the “very unusual situation” was “unsettling" for her and her staff.

“I am as interested as everyone else about their motives and purpose, which I hope will become clear as the investigation moves forward,” she said in a statement released Tuesday evening.

The parties used the incident as an opportunity to trade fire.

Michael McHale, chairman of the Louisiana Democratic Party, dubbed it a "Louisiana Watergate."

"Given his ties to some of the players involved, Sen. Vitter should immediately denounce the actions of these four men and anyone who may have instigated, supported or assisted them," McHale said.

Vitter has been critical of ACORN and called for an investigation into the community organization's practices in the wake of O'Keefe's videos showing ACORN Housing Corporation employees providing questionable counsel.

Vitter's office did not respond to a request for comment, but the National Republican Senatorial Committee said Democrats sounded desperate.

"When you consider that their candidate is trailing Senator Vitter by 18 points in the polls it's little wonder that his Democrat opponents are emphasizing the 'D' in desperation,” said Brian Walsh, a spokesman for the committee.

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 8:08 p.m.