It has been a rare point of consensus about the case brought by Georgia prosecutors against former President Donald J. Trump: the Fulton County district attorney, Fani T. Willis, probably made a mistake by having a romantic relationship with a co-worker.

But the agreement ends there.

As people in Atlanta and its suburbs digested gripping and emotional testimony, what they saw wasn’t just the behavior of Ms. Willis, but a test for their views on race, gender, justice and the city they call home.

Ms. Willis’s sharpest critics, backers of the former president, relished what they saw as the error that could pull her off the case — endangering, if not entirely torpedoing, a prosecution that some legal experts regard as one of the strongest ones against Mr. Trump.

The biggest fear of some of her supporters is that those critics are correct.

“I just wish she would’ve made better decisions,” said Andrea Maia, a recent college graduate living in Atlanta, who is otherwise sympathetic to and supportive of Ms. Willis. “I wouldn’t have done it.”

The testimony came as part of a hearing this week to decide whether Ms. Willis’s romantic and financial relationship with Nathan Wade, an outside lawyer she hired to help lead the prosecution, amounted to a conflict of interest and whether she should be removed from the case.