Once-prominent Philadelphia fund-raiser Robert M. Feldman has agreed to plead guilty to a misdemeanor campaign violation, in a federal case that ensnared the governor of Puerto Rico but yielded convictions only of some of his associates.

Feldman admitted in court papers that he helped conceal the source of $6,000 in campaign funds for the unsuccessful 2008 reelection campaign of Gov. Aníbal Acevedo Vilá.

Feldman was reimbursed by Cándido Negrón Mella, a Delaware County dentist who had reached the limit on contributions to the campaign. Such "conduit" contributions violate federal election law.

In return, prosecutors agreed to drop a felony case against Feldman that accused him and others of a much larger scheme: funneling more than $100,000 in illegal contributions to Acevedo Vilá in the hope of winning government deals.

Last year, prosecutors in Puerto Rico filed two indictments against Acevedo Vilá, the second three months before the election. He lost in a landslide.

But a federal judge dismissed more than half the charges against the former governor, ruling that prosecutors wrongly interpreted federal election laws. In March, a jury cleared him and his legal adviser of all counts.

Feldman's lawyer, Henry E. Hockeimer, declined to comment. Feldman's plea and sentencing hearing is scheduled for June 12.

Eight other defendants pleaded guilty to campaign-finance-related charges. The charges against Negrón Mella are pending.

Feldman, 61, an insurance and banking entrepreneur, was one of the most successful fund-raisers in Pennsylvania and New Jersey, raising millions for politicians including Gov. Rendell, former Mayor John F. Street, U.S. Sen. Bob Casey, and former New Jersey Gov. Jim McGreevey.

"I'm good at it and I love doing it," Feldman told a reporter in 2001.

He caught the attention of federal investigators after his close business associate, lawyer and power broker Ronald White, became the central figure in the sweeping City Hall corruption case.

The Puerto Rico investigation grew out of the City Hall probe. Feldman, who complained on wiretaps of being shut out of Philadelphia deals, was never accused of wrongdoing in that case or in investigations of pay-to-play practices in New Jersey.

Today, Hockeimer said, Feldman is semiretired. He is no longer involved in politics.

Contact staff writer Joseph Tanfani at 215-854-2684 or jtanfani@phillynews.com.