A judge in Georgia has ruled that the district attorney Fani Willis can continue to head the prosecution of Donald Trump for trying to undermine the 2020 presidential election in the state, as long as a top deputy steps down.

The ruling came after hearings that offered a dramatic deviation from the racketeering case against Trump and 14 remaining co-defendants as it investigated Willis’s romantic relationship with Nathan Wade, a special prosecutor in the case and her top deputy.

“The court therefore concludes that the prosecution of this case cannot proceed until the state selects one of two options. The district attorney may choose to step aside, along with the whole of her office, and refer the prosecution to the prosecuting attorneys’ council for reassignment,” Judge Scott McAfee, the judge overseeing the case, wrote on Friday.

He added that alternatively Wade can withdraw “allowing the district attorney, the defendants, and the public to move forward without his presence or remuneration distracting from and potentially compromising the merits of this case”.

Related: Is appearance of impropriety enough to oust Fani Willis from Trump case?

The question at the heart of the matter was whether Willis had a conflict of interest in the case because of her relationship with Wade. Michael Roman, one of the 14 remaining defendants in the case, filed a motion in January saying Willis should be disqualified from handling the case because of her romantic relationship with Wade, which was not publicly known at the time.

The two eventually admitted their relationship, but said it did not begin until 2022, after Wade was hired to work on the Trump case. Wade acknowledged that he paid for vacations for the two of them to places such as Napa in California and Aruba, but he and Willis both said she paid him back in cash.

McAfee said the arrangement presented the appearance of a conflict of interest, which was enough to warrant at least Wade’s removal.

“As the case moves forward, reasonable members of the public could easily be left to wonder whether the financial exchanges have continued resulting in some form of benefit to the district attorney, or even whether the romantic relationship has resumed,” he wrote on Friday.

“Put differently, an outsider could reasonably think that the district attorney is not exercising her independent professional judgment totally free of any compromising influences. As long as Wade remains on the case, this unnecessary perception will persist,” he added.

The hearing dived deeply into the personal lives of Wade and Willis, and featured dramatic testimony from Willis in which she bluntly accused Roman’s lawyers of lying and sought to regain control over one of the most high-stakes trials in America.

It also muddied the waters of the case – transforming a blockbuster prosecution about a criminal scheme to overturn the election into a salacious hearing about the love life of the district attorney. It was a transformation that Willis seemed keenly aware of when she took the stand in mid-February.

“You’re confused. You think I’m on trial. These people are on trial for trying to steal an election in 2020. I’m not on trial, no matter how hard you try to put me on trial,” she said.

The strongest testimony for defense lawyers came from Robin Bryant-Yeartie, a former friend of Willis’s who said the relationship between Wade and Willis began before Wade was hired. Willis’s lawyers cast Bryant-Yeartie as a disgruntled former employee of the district attorney’s office who had an axe to grind. No other witness corroborated her testimony.

The star witness for the defense was supposed to be Terrence Bradley, a former law partner of Wade’s. Bradley had told Roman’s lawyer that he knew the relationship began before Wade was hired, but when hetook the witness stand he refused to confirm what he said in text messages to her, and said he was only speculating.