A lawyer for one of former President Donald J. Trump’s co-defendants in the Georgia election case suggested on Friday that the two prosecutors leading the case had lied about when their romantic relationship started.

The defense lawyer, Ashleigh Merchant, said that a witness she hoped to put on the stand could testify that the romantic relationship between Fani T. Willis, the Fulton County district attorney, and the special prosecutor managing the Trump case, Nathan J. Wade, had begun before Ms. Willis hired Mr. Wade.

That would contradict Mr. Wade, who said in a recent affidavit that his relationship with Ms. Willis had not begun until 2022, after his hiring. The affidavit was attached to a court filing made by Ms. Willis.

Ms. Merchant identified the witness as Terrence Bradley, a lawyer who once worked in Mr. Wade’s law firm and for a time served as Mr. Wade’s divorce lawyer. “Bradley has non-privileged, personal knowledge that the romantic relationship between Wade and Willis began prior to Willis being sworn as the district attorney for Fulton County, Georgia in 2021,” Ms. Merchant’s filing, which came late Friday afternoon, states.

Ms. Merchant, on behalf of her client Michael Roman, a former Trump campaign official, is seeking to have Mr. Wade, Ms. Willis and Ms. Willis’s entire office disqualified from the Trump case. Ms. Merchant argues that the romantic relationship, as well as vacations the prosecutors took together that were paid for at least in part by Mr. Wade, amount to a conflict of interest.

“It is evident that the district attorney and her personally appointed special prosecutor have enriched themselves off this case,” Ms. Merchant wrote.