In a surprise move, Gov. Mike Easley’s former legal counsel and top aide Ruffin Poole pleaded guilty to one count of income tax evasion Monday in exchange for prosecutors conditionally dropping all other federal charges against him.

The move came two weeks after Poole pleaded not guilty to 57 corruption counts ranging from bribery and extortion to money laundering and racketeering. The plea agreement means that Poole is cooperating with federal investigators as they edge closer to possibly indicting Easley himself. It also means the Poole case will not go to trial if prosecutors are satisfied that Poole has provided prosecutors enough information about other targets of the investigation to justify dropping the remaining charges.

“I trust that Mr. Poole’s cooperation is going to be valuable, and I can promise that we will use the information to follow the evidence to wherever this investigation leads,” said U.S. Attorney George Holding, the lead prosecutor in the case.

The income tax charge stems from an investment Poole made in Cannonsgate, a high-end coastal development in Carteret County. Poole admitted that he didn’t disclose a $30,000 return from the investment on his federal income taxes for 2005. A press release (PDF) from Holding’s office also states that Poole’s $30,000 income resulted “from criminal activity” — suggesting that aspects of the transactions surrounding Cannonsgate, where Easley purchased a prime waterfront lot at a discount, violated the law.

The initial indictment, handed down in January, alleges that Poole, who garnered the nickname of “the little governor” in Easley’s office, derived significant personal benefits by using his official position to expedite environmental permits for coastal developers.

A federal grand jury issued six new counts in March, three of which related to income tax evasion.

The indictment alleges that Wilmington financier Lanny Wilson gave Poole several free vacations to Costa Rica, a bachelor party in New Orleans, and an engagement party in Wilmington. Wilson also allowed Poole to invest in two coastal developments — one of which was Cannonsgate — that netted Poole $55,000 in a short period of time.

Poole and his lawyer declined to comment while leaving the federal courthouse in Raleigh. The plea deal doesn’t prohibit other state or federal officials from prosecuting Poole.

Speaking to reporters outside the courthouse, Joe Sinsheimer, a former Democratic consultant turned open-government advocate, tied the corruption case to Easley’s successor, Gov. Bev Perdue.

“We have a state with over 9 million people in it, and Gov. Perdue chose Lanny Wilson to be the chairman of her campaign finance team,” Sinsheimer said. “It’s shocking that this level of corruption goes from one administration to the next.”

Poole faces up to five years in prison and up to $250,000 in fines. His sentencing hearing hasn’t been scheduled.

David N. Bass is an associate editor of Carolina Journal. Associate editors Sara Burrows and Anthony Greco contributed reporting to this story.