The petition for Mr. McCrary generated some publicity, and on Tuesday, he was released after an anonymous donor posted his bail.

Ms. Geraghty and her allies are now pressuring Atlanta to embrace a national wave of bail reform that has already taken hold in places like Chicago, Houston, New Jersey and, most recently, Alaska. Those who support reform argue that detaining the working poor over small bail amounts can ruin careers and disrupt families. They note that jail time racked up while waiting for a case to be resolved can sometimes exceed the jail time prescribed for the offense itself. They argue that such detentions violate the 14th Amendment’s equal protection clause, because it denies arrestees “the pretrial freedom made available to those who can pay for release for the same offense,” as Ms. Geraghty wrote in her petition.

And, they say, bail does nothing for public safety, using access to money rather than potential for danger to determine who goes free. “This is the right time for Atlanta to move away from wealth-based detention,” Ms. Geraghty said.

Earlier this month, the Southern Center for Human Rights in Atlanta joined Civil Rights Corps, based in Washington, in sending a letter to Atlanta’s new mayor, Keisha Lance Bottoms, asking her to lead a change in the city’s bail system. The groups noted that they had forced changes in other Georgia cities by suing them.

But Atlanta already appears ripe for change. Ms. Bottoms has spoken candidly, and movingly, about the conviction of her father, the R&B singer Major Lance, on cocaine charges in the 1970s. “I learned very early on that good people sometimes make bad decisions,” she said in a biographical campaign video. Ms. Bottoms has pledged, in her agenda for her first 100 days in office, to create a criminal justice reform commission.