George Santos' former campaign treasurer pleads guilty to one count of conspiracy to defraud the United States

The former campaign treasurer for New York Rep. George Santos pleaded guilty Thursday to one count of conspiracy to defraud the United States by committing one or more federal offenses.

Nancy Marks, a veteran GOP operative, oversaw the campaign's finances for the Long Island Republican before being dismissed after a series of filing abnormalities led to allegations of wrongdoing against her and the candidate.

The case against Marks has the same court docket number as listed for Santos' case - an indication that the charge against her is directly related to her work for the scandal-tarred House freshman. Her decision to plead guilty - implicating Santos in at least one crime in the process - offers a fresh reminder to voters in the competitive 3rd Congressional District, which could be key to Republicans retaining their narrow House majority next year, of the breadth of Santos' alleged wrongdoing.

Marks' attorney, Raymond Perini, said his client does not have a cooperation agreement with the government "at this time."

"If we get a subpoena, we'll do the right thing," he said.

Addressing the question of why Marks helped Santos, Perini said there was "a manipulation involved that had to do with her family and the death of her husband."

Marks will pay a $100,000 bond for release. She faces a maximum sentence of five years in prison. She is due back in court on April 12.

Speaking calmly in court, Marks said she and Santos knowingly filled out federal documents with false claims and information.

"I filed a first quarter 2022 report stating that $500,000 was loaned to the campaign by co-conspirator #1 and the money was not received at the time," Marks said during her allocution - a defendant's formal address to the court. "As campaign treasurer, I knew that the loan had not been made at the time."

Perini identified "co-conspirator #1" as Santos, whose own attorney, Joe Murray, was present in court for the entire hearing. Murray had no comment on the proceedings.

Santos has faced persistent questions about six-figure loans that Federal Election Commission records show him having made to his campaign - despite the New York Republican apparently lacking the means to self-finance a congressional bid. And media outlets have found examples of donors listed on the Santos campaign's FEC reports who could not be located at the addresses reported in the filings.

"I did these things in agreement with co-conspirator #1," Marks said Thursday, "for his benefit and to obtain money for his campaign by artificially inflating his funds to meet thresholds set by a national political committee."

Perini noted that Marks had never faced serious allegations of wrongdoing before coming into contact with Santos.

"This man, with his lies and manipulation, has ruined many a life," Perini said. "Nancy Marks was a well-respected campaign treasurer and political operative. She's helped a lot of young clients do a lot of good things."

Marks, who is well-known to GOP candidates on Long Island, previously worked for former New York Rep. Lee Zeldin, who unsuccessfully ran for governor in 2022. Zeldin distanced himself from his longtime bookkeeper earlier this year, saying she would not oversee finances for a planned federal PAC in light of the irregularities surrounding her work for Santos.

But Marks' ties to Santos extended beyond filing compliance reports with federal regulators. She was also paid for fundraising services, federal records show. In addition, state records in Florida show that companies tied to her and Santos were stakeholders in a for-profit enterprise established shortly after the Republican launched his 2022 congressional bid.

Santos in May pleaded not guilty to 13 federal charges, including seven counts of wire fraud, three counts of money laundering, one count of theft of public funds and two counts of making materially false statements to the US House of Representatives.

Despite those charges and the uproar over his assorted lies and exaggerations about his personal life, Santos remains in Congress and has announced he is running for reelection next year. Several Democrats and Republicans have already filed to challenge him.

This story and headline have been updated.

CNN's Fredreka Schouten contributed to this report.