Mark Greenberg is crying foul over tactics being used by a variety of Democratic organizations working to support the re-election of 5th District U.S. Rep. Elizabeth Esty.

The Litchfield Republican, challenging Esty’s bid for a second term, says he has been the victim of “push polls” — telephone calls that spread negative attacks about a candidate under the guise of being a legitimate research survey.

Esty’s campaign has emphatically denied involvement in or knowledge of push polls, but a common narrative has emerged in the way that Esty’s campaign, the Democratic Congressional Campaign Committee, the House Majority PAC, and the Connecticut Democratic State Central Committee have attacked Greenberg.

Material used in the “push polls” Greenberg cites mirrors information included in a 99-page “opposition research book” prepared by the DCCC. Some of it has also been used in a voter guide and TV ads aired by the House Majority PAC, the DCCC, and the Esty campaign itself, including a persistent line of attack on Social Security that the Hartford Courant has labeled “false.”

According to the Hartford Courant’s Jon Lender, some of the information in that research book was based on the wrong Mark Greenberg and real estate companies with similar names but not connected to the candidate.

One of the push polls that has attacked Greenberg talks about a child being affected by lead paint in one of his buildings. But it was based on faulty DCCC research and was related to a landlord with no connection to Greenberg.

Esty’s campaign and the House Majority PAC both denied involvement in “push polls” in the 5th District. Marc Brumer, a spokesman for the DCCC, would not comment on the organization’s polling operations, and also refused to comment on Lender’s reporting.

“We certainly poll, which is what we use to inform what spending we do in various races and what messages work best,” said Matt Thornton, a House Majority PAC spokesman. “But push polling is not something we spend money on.”

Polling experts say that “message testing” typically includes both pro and con statements about multiple candidates, whereas a “push poll” focuses on one candidate and includes information that’s “uniformly negative.”

Greenberg himself was accused of using push polling to attack former state Sen. Sam Caligiuri in a previous unsuccessful Republican primary bid for the 5th District in 2010.

In denying involvement, Esty and her campaign spokeswoman, Laura Maloney, have criticized push polls as a dirty tactic that is “ineffective” and a “waste of money.”

Push polls are actually against the law in New Hampshire, where Mountain West Research, the firm Greenberg Campaign Manager Bill Evans says is behind some of the push polling used in the 5th District, has been subject to fines.

While unaware of the specific controversy over push polling in the 5th District, Gary Rose, chairman of the political science department at Sacred Heart University, said that it’s hard to believe such tactics could be used by surrogates without a candidate’s knowledge.

“If in fact it’s taking place . . . the candidate has to know about it,” he said. “Any time a push poll is done, it’s coming right out of the headquarters, it’s got to be. And if it’s not coming from headquarters, it’s coming from a group closely associated and coordinating with the campaign . . . you can’t tell me the candidates aren’t being somewhat consulted.”

It would be illegal for a candidate to “coordinate” with independent groups spending money on a congressional race, so campaigns are typically careful to keep PACs supporting them at arms’ length.

Rose called it a “fraudulent law” and said that the shuttling back and forth of key operatives between campaigns and independent groups makes it hard to believe that’s really happening.

For example, Julie Sweet served as campaign manager for Esty’s bid for Congress two years ago and then as her congressional office chief of staff until January of this year. She now works for the DCCC, which prepared the opposition research book on Greenberg and has spent hundreds of thousands of dollars attacking him and supporting Esty’s candidacy.

Esty’s campaign rejects this assessment.

“Contrary to Mark Greenberg’s false allegations and other people’s opinions, we had nothing to do with this,” Maloney said. “Our campaign follows all election laws and maintains high internal standards. Mark Greenberg has been running for Congress for six years. He knows full well we have nothing to do with that book, and our campaign would never use push polls and condemns anyone who does. This is just another desperate attempt by Mark Greenberg to distract from his extreme views and questionable business practices.”

Early in this year’s campaign, Esty turned down a Greenberg proposal that would have had both candidates rejecting involvement by outside groups. It was similar to a pledge that Scott Brown and Elizabeth Warren abided by in a race for the U.S. Senate in Massachusetts two years ago.

Esty said that she couldn’t agree to that when Greenberg has a personal net worth in the tens of millions of dollars and the ability to “self-fund” his campaign. With two weeks left before the election, however, Esty had outspent Greenberg by more than 2 to 1, not including the hundreds of thousands of dollars spent on her behalf by the DCCC, House Majority PAC, and the Connecticut state Democratic Party.