ALBANY—Federal prosecutors' unexpected request to dismiss a charge against western New York political operative G. Steve Pigeon for allegedly orchestrating an illegal campaign donation to Gov. Andrew Cuomo may signal that there was insufficient evidence to prove the charge, a defense attorney said Wednesday.

Pigeon, the former chairman of the Erie County Democratic Party with heavy ties to New York's top Democrats, pleaded not guilty Friday to an eight-count indictment alleging that he bribed a state Supreme Court justice.

But in a surprise move Friday, federal prosecutors in Buffalo asked U.S. Magistrate Judge Michael Roemer to dismiss another charge filed against Pigeon in April that had accused him of orchestrating an illegal $25,000 donation from foreign national with ties to the gaming industry to Cuomo's re-election campaign.

Roemer agreed to dismiss the bribery charge without prejudice, meaning that prosecutors can opt to refile it at a later date. A request for comment as to why federal prosecutors dropped the charge did not receive a response from a spokeswoman for the U.S. Attorney's Office in the Western District in Buffalo.

Pigeon's attorney, Paul Cambria, a senior partner at Lipsitz Green Scime Cambria, did not return calls and emails seeking comment this week. Cambria had told reporters in Buffalo Friday that the charge was dropped because they were “bogus.”

“I have always felt that particular case was bogus, and I have said so,” Cambria said, adding that  he believes the federal charges were filed because Attorney General Eric Schneiderman's state case against Pigeon is on shaky ground after a state Supreme Court justice ruled to suppress email evidence that helped Schneiderman's office secure an indictment on state charges against Pigeon last June.

A spokeswoman for Schneiderman responded via email that “we intend to vigorously pursue our prosecution and ultimately prevail.”

Attorney Michael Farkas, who has his own practice in New York City, told the New York Law Journal Wednesday that the charges may have been dropped because they couldn't be proved. Farkas, who is not connected with the Pigeon case, represented former Assemblyman Nelson Castro, who secretly aided state and federal investigators in helping secure public corruption charges against legislators.

“It is possible that the state judge's suppression ruling substantially undermined the government's ability to pursue the illegal donation charge, or that the charge simply couldn't be proven at all.  It's also possible that maintaining the illegal donation charge could permit the defense to introduce favorable evidence at trial that the government could otherwise avoid if the charge was dismissed.  We will have to wait for the real reasons to come to light,” Farkas said in an email.

Pigeon and Schneiderman, who brought separate charges against the Democratic operative in April over allegations of illegally coordinating with candidates benefiting from a political action committee, have a contentious history. Pigeon had been of counsel to former state Sen. Pedro Espada, who was largely responsible for sending the upper chamber into chaos during the  2009 Republican takeover of the state senate. Pigeon has been credited for being the brains behind the Senate coup at a time when Schneiderman was serving as a member of the Senate Democratic conference.