Before he became the special prosecutor leading the Georgia election interference case against former President Donald J. Trump, Nathan Wade was working as a private defense lawyer and a judge for a municipal court in the Atlanta suburbs.

Now, Mr. Wade is accused of being romantically involved with the district attorney who hired him in 2021, Fani T. Willis. A court filing this week suggested their relationship was the reason she chose Mr. Wade for the high-paying job.

The filing, from a lawyer for one of Mr. Trump’s co-defendants, said that Ms. Willis and Mr. Wade had then used some of his earnings, which so far total more than $650,000, to vacation together in places including Napa Valley and the Caribbean.

Mr. Wade was largely unknown when Ms. Willis selected him to lead one of the highest-profile prosecutions in American history.

In the late 1990s, he was employed for about a year by the Cobb County Solicitor’s Office, which prosecutes misdemeanors and traffic citations. He appears to have had little prosecutorial experience beyond that, until now.

Later, as an associate judge in Marietta, an Atlanta suburb of about 60,000 residents, Mr. Wade presided over cases dealing with some misdemeanor crimes, traffic tickets, and violations of city ordinances.