Ms. Marks did not immediately respond to a request for comment. A lawyer for Mr. Santos, Joseph Murray, said that “in light of the complaints filed with the F.E.C., it would be inappropriate” to respond.
Hours before Ms. Marks’s letters were made public, Mr. Santos had already acknowledged the pressure he faced over his campaign finances, saying he would temporarily step aside from his positions on congressional committees in light of “both my personal and campaign financial investigations.”
Even as Mr. Santos has received headlines over revelations that he invented family ties to the Holocaust and 9/11, Ms. Marks has drawn attention of her own. An experienced political operative who served as treasurer on former Representative Lee Zeldin’s unsuccessful campaign for governor, Ms. Marks has been with from Mr. Santos since his first run for office, assisting with accounting and raising money.
Her involvement extended beyond Mr. Santos’s campaign, records show. Florida corporate records from May 2021 show that a company called R.I.A. Concepts Holding, which uses Ms. Marks’s home address, was one of the stakeholders in Mr. Santos’s new venture, Red Strategies USA.
Mr. Santos formed the company, which has been described as a political consulting group, along with his colleagues from his former firm, Harbor City Capital, after its assets were frozen as part of a Securities and Exchange Commission lawsuit that accused it of operating a Ponzi scheme. Neither Mr. Santos nor his business partners were named in that action.
Red Strategies USA has since been dissolved for failing to file a financial report.
Ms. Marks’s resignation comes as the Santos campaign is facing increased scrutiny. Last week, the magazine Mother Jones reported that the identities of more than a dozen of the major donors to Mr. Santos’s campaign could not be confirmed. The Miami Herald reported that several of his campaign expenditures did not match the records of those vendors. And last year, The Times reported the campaign had spent thousands of dollars on rent and a bizarre string of payments for $199.99 — one cent below the threshold at which F.E.C. rules require that candidates provide receipts.
This irregularity, among others, formed the basis of a complaint that the Campaign Legal Center filed with the F.E.C. earlier this month. That complaint accused Mr. Santos of using campaign funds for personal expenses and of conducting a straw donor scheme to obscure the source of $705,000 he lent to his campaign.
