Attorneys for Congressman Chaka Fattah attacked the credibility of a key prosecution witness in his corruption trial Thursday, getting the political consultant to concede he was not always honest with family, friends and colleagues.

The admission came on the fourth day of testimony in the federal corruption trial against the 11-term congressman and four of his associates. Each is charged with an array of RICO violations, ranging from conspiracy to bribery to money laundering and bank fraud, in what is expected to be an eight-week trial.

Testifying for a second day Thursday, Thomas Lindenfeld, who pleaded guilty to wire fraud in 2014 and has agreed to cooperate with the government in exchange for a lighter sentence, barely gave Fattah, his former longtime colleague and confidant, a glance.

RELATED: Key witness against Fattah in corruption trial testifies loan was illegal

“You admitted you committed a federal crime – a scheme to commit fraud. You knowingly participated in a conspiracy,” defense attorney Samuel Silver, pressed Lindenfeld under cross-examination.

“Did you even deceive your wife … in any way?”

“I didn’t tell her the whole truth, no,” said Lindenfeld.

Prosecutors contend that Fattah, Lindenfeld, and another government witness, Gregory Naylor, as well as other co-conspirators, engaged in a scheme to violate the local campaign finance laws during Fattah’s race for mayor of Philadelphia in April 2007.

Allegations in the government’s indictment assert Fattah arranged for an illegal $1 million campaign loan from Al Lord, the wealthy CEO of the student-loan giant Sallie Mae. To conceal this loan, prosecutors say Fattah and Lindenfeld routed the money from Lord through Lindenfeld’s political consulting firm, LSG.

On cross-examination, Silver sought to show Lindenfeld's testimony was an attempt to spare himself a long prison sentence.

“You face a maximum penalty of 20 years in prison as a result. You’re 61 years old. You could be in there until you’re 81 if you don’t get leniency,” he said.

On Wednesday, Lindenfeld admitted he had doubts about Fattah’s ability to raise campaign funds, yet he accepted Lord’s loan money despite that. He said he expected Fattah to pay back that loan because he trusted him.

RELATED: Prosecutor calls Chaka Fattah a thief as racketeering trial gets underway

“You put your company on the line. Your company was in dire straits. The campaign was desperate for funding, right?” asked Silver.

“At the time, you knew you were involved in a fraudulent scheme?”

“Yes,” said Lindenfeld.