A guilty plea from a former top aide to U.S. Rep. Chaka Fattah (D., Pa.) has set Philadelphia political circles abuzz with speculation on what the congressmen might have known about the man's crimes and what role, if any, he might have played.

But one voice was notably absent from that conversation Thursday: Fattah's.

The normally outspoken congressman, who has previously denied any wrongdoing in connection with the federal investigation that ensnared his aide, was suddenly mum.

Thursday marked a second day of silence since the filing of court documents that detail his former chief of staff's handling of an illegal $1 million campaign donation. The documents, replete with allegations about an unnamed "Elected Official A," suggest that a continuing investigation may lead to Fattah's door.

Fattah's spokeswoman declined to comment Thursday, as did his lawyer, Luther E. Weaver 3d, who said he did not expect the congressman or his staff to have anything to say about the ongoing probe any time soon.

Meanwhile, Fattah's Twitter and Facebook accounts continued with their usual churn of news releases and announcements of new projects and grants, with nary a nod to the scandal unfolding within his inner circle.

Among the postings Thursday were tweets touting the success of President Obama's health care initiatives, a news story on how quickly babies' brains develop, and a campaign ad.

Highlighting the values that have guided him throughout his two decades in Congress, Fattah appears in the spot alongside President Bill Clinton and Obama.

"Throughout my career, I have been an advocate for children and working families," he says in the ad, created for his November reelection race. "It's a great privilege to represent my home city in the United States Congress."

The man at the center of the federal investigation, Fattah's former aide, Gregory Naylor, has also remained silent. But in his plea agreement with prosecutors, Naylor admitted that he and his boss - "Elected Official A" - conspired to pay off a series of debts, including an unreported $1 million campaign donation, with federal grant money and political contributions funneled through a series of nonprofits and consulting firms.

In a separate scheme, Naylor said, he helped steer $22,000 in campaign funds to covertly pay down the college loans of the elected official's son.

"Elected Official A and others orchestrated the theft of federal grant funds and other charitable funds," the document said.

Prosecutors have declined to identify the official. But their descriptions in court documents leave little doubt that it is Fattah.

Much of the case against Naylor centered on his work for the official during the 2007 Philadelphia mayor's race, in which Fattah ran and lost. Naylor served as his chief strategist during that race.

Court filings also reference a lawsuit the official filed that year challenging the city's $5,000 cap on individual campaign contributions. Fattah lost such a suit in Superior Court.

Even as Naylor was pleading guilty Wednesday to counts of concealing a felony, falsifying documents, and lying to the FBI, Fattah kept up a full day's schedule of appearances around Philadelphia, showing no sign that anything else was on his mind.

He started his day just off the Benjamin Franklin Parkway, gathering with the business elite and city officials to break ground on a $160 million luxury apartment complex. Smiling and at ease, he joked with project leaders and offered congratulations to those involved.

The announcement of a $260,810 National Science Foundation grant at the University of Pennsylvania followed.

Fattah's reluctance to discuss the allegations marks something of a reversal. He has rarely demurred from discussing the investigation in the past.

When prosecutors subpoenaed documents from his congressional office in the spring, Fattah shot back, suggesting there were "improprieties in the conduct [of investigators] that could even stretch to illegalities."

Asked at the time whether he had been notified that he was a target of an investigation, he paused until his chief of staff interjected, "No."

"No," the congressman added. "Let's try that again - no, no, no, and no."

When his 31-year-old son, Chaka Jr., was charged this month with multiple counts of bank and tax fraud - a case the younger Fattah linked to the investigation of his father - the congressman again responded with a full-throated defense.

He questioned Assistant U.S. Attorney Paul Gray and FBI agent Richard Haag's handling of the case, saying he had concerns about "the fair administration of justice."

But even as Fattah remained silent Thursday, others felt compelled to speak out.

Armond James, his Republican opponent in what had been considered a quiet reelection race, attacked Fattah.

"The interests of the citizens of the Second Congressional District have been ignored in favor of personal financial gain, and our resources taken," he said. "Congressman Fattah has failed us all."

In Washington, Democratic mayoral candidate Muriel Bowser on Thursday fired her nationally renowned campaign strategist, Thomas Lindenfeld, a longtime Fattah ally, and suggested that he was an unnamed coconspirator in the Naylor case.

Though documents in the Naylor case describe a Washington-based consultant who helped arrange the $1 million contribution to Fattah's mayoral campaign and later laundered the grant money stolen to repay it, prosecutors have declined to identify the man.

In a statement first reported by Washington City Paper, Bowser said: "I'm quite surprised by the allegations out of Philadelphia. I have the highest expectations of transparency from my campaign team; Tom no longer has a role on the campaign."

Lindenfeld did not return calls seeking comment.