A top political strategist for U.S. Rep. Robert Brady on Friday became the latest defendant to admit his role in a scheme to illegally cover up $90,000 the congressman's campaign paid a 2012 primary challenger to drop out of the race.

Donald "D.A." Jones pleaded guilty to charges of lying to federal agents and agreed to cooperate with the ongoing investigation in a brief hearing in federal court in Philadelphia.

His admission of guilt is the first to come from within Brady's camp in a case that already has wrung guilty pleas from the congressman's 2012 opponent – former Municipal Court Judge Jimmie Moore – and the judge's former campaign manager.

"I accept full responsibility for my actions and consider my guilty plea a first step in making amends," Jones said in a statement issued by his attorney Alan J. Tauber after the hearing. "I apologize to the people of Philadelphia and to my family for bringing this dishonor upon them."

What Jones' plea means for Brady – one of the longest-serving congressmen in the state and the powerful head of Philadelphia's Democratic Party – remains unclear.

For months, federal investigators have signaled that they were building a case against the 10-term incumbent. But last month, prosecutors allowed an agreement preserving their right to charge Brady outside the traditional statute of limitations to lapse, raising questions about their willingness to move forward with a case.

Brady's lawyers took that development as a sign that their client might be in the clear, although they cautioned at the time that there were still some related charges that fell within federally mandated time limits that prosecutors could pursue if they felt they had the evidence to prove them in court.

It was not immediately clear how Jones' guilty plea might complicate their thinking. Brady's lawyers, James Eisenhower and Ronald Levine, declined to comment Friday but have consistently maintained that their client did nothing wrong.

In the deal he struck with prosecutors, Jones, 62, of Willingboro, N.J., agreed to testify if needed against Brady or Ken Smukler, another of the congressman's strategists who was indicted in October on charges including conspiracy and making an unlawful campaign contribution.

In a series of terse responses to U.S. District Judge Jan E. DuBois, Jones admitted that he had conspired to hide payments from Brady's campaign and later had lied about it to the FBI – a charge that carries a maximum prison term of up to five years.

Jones also said Friday that he had agreed to plead guilty in an unrelated case brought against him in the Western District of Missouri.

Details of that matter remain under seal and Tauber, Jones' lawyer, declined to discuss the case.

Jones, known in Philadelphia political circles as a low-key technocrat experienced in get-out-the-vote efforts, also has worked for other candidates including former City Controller Jonathan Saidel and Sheriff Jewell Williams in recent years.

His plea agreement laid out a narrative that has become familiar since the FBI probe of the Brady matter emerged into public view this summer.

According to the document, Moore agreed to drop his primary campaign against Brady in 2012 after the congressman pledged to help him retire some of his considerable campaign debt – including more than $80,000 the former judge had personally loaned his own campaign.

Because federal campaign contribution limits at the time capped the amount that one candidate could give another campaign at $2,000 for a primary election, Smukler and Jones agreed to funnel the money from Brady's campaign coffers to Moore's by routing it through consulting firms they owned, the plea document says.

In Jones' case, that included a $25,000 payment that his consulting firm – D. Jones and Associates – passed through to Moore's campaign manager, Carolyn Cavaness, for alleged consulting services.

But both Jones and Cavaness have admitted that she did no work for Jones' company to earn that money and that invoices she prepared were a ruse to cover the real reason for the payments.

Prosecutors say Smukler funneled the remaining $65,000 through his consulting company to Moore, disguised as a payment for polling data the judge had commissioned before dropping out of the race – information Brady already had obtained.

Both Smukler and Brady have defended the poll's purchase, claiming that they were paying for exclusive rights to the information and to keep it out of the hands of future challengers to the congressman.

Smukler has denied the charges against him and vowed to take his case to trial.

Moore and Cavaness have pleaded guilty to charges of filing false campaign reports and are cooperating with investigators.