President Trump denied the allegations. He called Ms. Carroll a liar, intent on selling a new book. He said he had never met her, despite a photo of the two of them together in the 1980s. He told reporters that he would not have assaulted Ms. Carroll because she “is not my type.”

Now Ms. Carroll, a journalist and columnist for Elle Magazine, has sued Mr. Trump for defamation, saying in a lawsuit filed in state court on Monday that Mr. Trump had damaged her reputation and her career when he denied her allegation in June.

His statements about Ms. Carroll, the lawsuit said, “are fully consistent with his tried-and-true playbook for responding to credible public reports that he sexually assaulted women.”