A day after Mayor Eric Adams visited President-elect Donald J. Trump in Florida, his lawyer filed court papers in the mayor’s federal corruption case arguing that the former prosecutor who brought the case was trying to advance his own political career.

The lawyer, Alex Spiro, wrote a letter on Saturday to the judge overseeing the case, arguing that a recent opinion article by the former prosecutor, Damian Williams, could prejudice the jury pool against Mr. Adams and was part of Mr. Williams’s plan to run for mayor or another political office.

“The conclusion here is inevitable,” Mr. Spiro said. “Mr. Williams brought a meritless case against a political rival to bolster his own immediate candidacy for office, potentially including mayor of New York.”

Mr. Williams announced the indictment against Mr. Adams in September, when he was the U.S. attorney for the Southern District of New York; he resigned in mid-December. He argued in the opinion article, published last week in City & State, that the city was in “deep crisis” and was “being led with a broken ethical compass.”

The piece did not directly mention the prosecution of Mr. Adams. But its publication, along with a new website highlighting Mr. Williams’s achievements, got New York’s political world buzzing, with some wondering whether he might run for office, most likely governor.

Mr. Williams did not immediately respond to a request for comment. Nicholas Biase, a spokesman for the Southern District, declined to comment.

Mr. Adams, a Democrat, is running for a second term in a competitive primary in June. He is set to go on trial in April on charges of bribery and fraud. He has insisted that he is innocent and has pleaded not guilty.

Mr. Trump has said that he is considering offering a pardon to Mr. Adams, arguing that both he and the mayor were “persecuted” by prosectors. The two men had lunch at the Trump International Golf Course in West Palm Beach on Friday; Mr. Adams said they did not discuss his legal case.

Mr. Spiro asked the judge to consider Mr. Williams’s actions as part of the mayor’s efforts to have the case dismissed, and he called for the Department of Justice to open an investigation into whether the mayor’s prosecution had been brought for improper purposes.

Mr. Spiro argued that the “taint on the jury pool is irrevocable” and that Mr. Williams had “smeared Mayor Adams’s reputation for his own political benefit.”

Mr. Williams served as the U.S. attorney for the Southern District from 2021 to 2024 and oversaw many prominent cases, including prosecutions against the former New Jersey senator Robert Menendez and the rapper Sean Combs. Before he was appointed to the post by President Biden, he served as an assistant U.S. attorney in the office for nine years, leading the securities fraud unit for part of that time. He announced recently that he would join the law firm Paul, Weiss, Rifkind, Wharton & Garrison as a partner in the litigation department.

Mr. Trump has picked Jay Clayton, the top Wall Street enforcer during his first administration, to replace Mr. Williams. Mr. Clayton still must be confirmed by the Senate.

Benjamin Weiser and William K. Rashbaum contributed reporting.