Mr. Stringer, the former New York City comptroller, said that a woman’s claims of sexual assault were lies and caused “irreparable harm” as he ran for mayor.Nearly 20 months after allegations of unwanted sexual advances derailed his campaign for New York City mayor, Scott M. Stringer sued one of his accusers for defamation on Monday, arguing that she smeared his reputation with falsehoods and misrepresentations.In a lawsuit filed in State Supreme Court in Manhattan, Mr. Stringer said that the woman, Jean Kim, had done “irreparable harm to him and his political future” by portraying what he called an “on-and-off” consensual relationship as predatory. He demanded that Ms. Kim retract her accusations and pay damages.“These defamatory statements have caused Mr. Stringer emotional pain and suffering, as well as injury to his reputation, honor and dignity,” lawyers for Mr. Stinger, a longtime Democratic politician and former New York City comptroller, wrote in the 12-page complaint.The legal action appears to be a calculated risk for Mr. Stringer, 62. If successful, it could help clear up his public image as he contemplates a political comeback. But it also serves to resurface Ms. Kim’s decades-old claims of misconduct, while posing the risk of an embarrassing legal defeat and reopening scrutiny into an earlier chapter in his life.Defamation cases are notoriously hard to prove, especially for public figures. To even get his case heard in court, Mr. Stringer must get around New York’s statute of limitations for defamation, and his lawyers are relying on a relatively novel legal theory to do so.They wrote in the suit that the matter was reopened legally in August 2022, when they assert — with scant detail — that Ms. Kim caused Representative Carolyn Maloney to resurface her defamatory statement against Mr. Stringer.The factual and legal issues are particularly relevant at a moment when New York and the country are still grappling with balancing the claims of women propelled by the #MeToo movement against the right to due process, and appraising what should happen to public figures like Mr. Stringer who are accused of misconduct decades after the fact.Ms. Kim and a lawyer who had represented her during the mayoral campaign did not comment on Monday morning, after the suit was filed.In an interview on Friday, Mr. Stringer said that he decided to take legal action now, after a needed “cooling-off period” for his family, to salvage his reputation. He acknowledged that waiting so long after the initial statements may have constrained his options legally.“There are times you could just walk away,” Mr. Stringer said. “But it was a lie. It was just a total lie. And I can’t live with myself if I did not do everything in my power to expose it.”Ms. Kim came forward in April 2021, in the heat of the Democratic primary for mayor. At the time, Mr. Stringer, a liberal who had slowly risen through the ranks of city politics, was considered a top-tier candidate for the nomination, though he seldom led early public polls.In a news conference and media interviews, Ms. Kim said that Mr. Stringer sexually assaulted her in 2001 when she was working as an unpaid intern on his unsuccessful campaign for public advocate. She said Mr. Stringer, then a state assemblyman whom she viewed as an older mentor figure, repeatedly groped her without consent, put his hands down the back of her pants, pressured her to have sex — and then warned her not to tell anyone.“He constantly reminded me of his power by saying things like, ‘You want me to make a phone call for you to change your life,’ ‘You want me to make you the first Asian district leader,’” Ms. Kim later told The New York Times. Many prominent supporters quickly backed away from his campaign. Mr. Stringer stayed in the race, but ultimately finished fifth in a primary election won by Eric Adams, who went on to become mayor.Mr. Stringer disputed Ms. Kim’s account, saying they were peers and that their relationship had been consensual and public within the tight circles of Upper West Side Democratic politics. His campaign also presented documents that showed that Ms. Kim, who has worked as a political lobbyist, might have helped one of Mr. Stringer’s rivals, Andrew Yang, which she disputed.Monday’s lawsuit largely repeats the conflicting stories without new evidence, and seeks to highlight factual errors or inconsistencies in Ms. Kim’s claims.It remains unclear if Ms. Kim’s version of events can be independently corroborated; she has not provided any records, nor has she mentioned associates with whom she discussed the allegations at the time.Defamation, particularly cases involving public figures like Mr. Stringer, can be difficult to prove, and the contradictory claims by Ms. Kim and Mr. Stringer — involving shifting sexual and romantic mores, political power and few hard pieces of evidence — only add to that burden.Mr. Stringer appears to have even more pressing legal burdens, with Ms. Kim likely to argue for dismissal because her original statements fall outside New York’s statute of limitations.His argument that the timeline was restarted in August rests on photos on social media that apparently show Ms. Kim at a campaign event with Ms. Maloney, who was running in a primary contest against Representative Jerrold Nadler, a longtime mentor of Mr. Stringer’s.Two weeks later, the congresswoman attacked Mr. Nadler in The New York Post for supporting “a man accused of sexual assault.” The lawsuit argues that it should have been “reasonably foreseeable” for Ms. Kim that Ms. Maloney would “republish” her claims after their meeting.Some allies of Mr. Stringer, left, believe he should be considered a potential heir to his mentor, Representative Jerrold Nadler, right, if he decides to retire.Hiroko Masuike/The New York TimesLegal experts briefed on the issues raised by the case, though, said that the application of the theory known as “republication” would be ripe for challenge on multiple grounds. Though the suit insinuates that Ms. Kim somehow prompted Ms. Maloney’s statement, Mr. Stringer’s lawyers never actually state what, if anything, she told the congresswoman to encourage or direct her to reference Mr. Stringer. “If there’s no clear evidence that the defendant directed the third party to make the statement, it’s fairly likely the case would be dismissed,” said Lee Levine, a retired media lawyer with decades of experience litigating defamation cases, including some for The Times.Though The Times reviewed a draft of the complaint before it was filed, it agreed with Mr. Stringer not to share details of the case with Mr. Levine or anyone else ahead of time.Mr. Stringer and his lawyers were clearly aware of the statutory limits. The suit filed on Monday made no mention of a second woman, Teresa Logan, who followed Ms. Kim’s allegations by accusing Mr. Stringer of kissing and groping her at a bar he helped found in the 1990s. That instance, Mr. Stringer conceded, was clearly outside the statute of limitations.Mr. Stringer said in 2021 that he had “no memory” of the woman but added that if they had met, he was sorry to have made her uncomfortable.If the case proceeds, Mr. Stringer and his allies believe the discovery process will turn up new and relevant information related to Ms. Kim’s actions and whether she coordinated her public statements with any of his political rivals.Mr. Stringer is represented in the suit by Milton L. Williams Jr., a former federal prosecutor and white-collar criminal defense lawyer who currently serves as the chair of the New York City Conflicts of Interest Board.After his loss, Mr. Stringer finished out his term as comptroller last December and began a consulting practice. But he almost immediately began discussing a political comeback.He went as far as to briefly campaign for a State Senate seat in Manhattan this spring, but he never actually entered the race. Allies still believe he should be considered a potential heir to Mr. Nadler should the congressman decide to retire.Still, the accusations of misconduct would almost certainly complicate any effort to return to public office.“Right now, I don’t have any plans to run for office. It’s something I’m not ruling out someday,” Mr. Stringer said. “This lawsuit is what’s in front of me at the moment.” More