“I’ve always fought for kids on both sides of the gun,” Johnson-Harrell said. “Young people who cause crimes are often victims themselves, even victims of a broken society.” This was how Keir Bradford-Grey, the city’s chief public defender, talked about her “clients” and the need to stop the destructive cycle of crime. But Johnson-Harrell worked for the Philadelphia D.A. — and as the leader of the office’s victims unit, she was saying the very word “victim” was in play. Johnson-Harrell explained that she was pushing diversion programs, restorative justice and reconciliation for both victims and defendants. “That way we reduce recidivism and crime,” she told me. “Isn’t that the job of the D.A.’s office?”

That question, of course — of what job district attorneys can or should do — was anything but settled. Krasner and other recently elected progressive prosecutors were proof of the uncertainty. In June, Krasner’s office released a statement that it had secured guilty verdicts or guilty pleas in 70 of the 85 homicide cases it tried in court, as if it were necessary to point out that the D.A. was still fighting crime. And in October, Krasner made a show of announcing a lengthy drug-trafficking investigation led by his office, which resulted in 57 people charged. Ben Waxman said they weren’t embracing “law and order” tactics or claiming that convictions were the only measure of success. But there was misinformation out there that Krasner, as a result of his policy changes, was letting all the murderers and drug dealers go. “You can push for sweeping criminal-justice reform while also efficiently prosecuting serious violent crimes,” Waxman told me.

For Bradford-Grey, the most radical difference over the past year was that she now had a willing partner in the district attorney. She and Krasner worked together on “big-picture” issues, and her defense attorneys had come to trust their counterparts enough to share vital information about clients earlier in the legal process, believing that prosecutors would use the information to make more individualized decisions. Bradford-Grey said Philadelphia still had a long way to go in what she called “this era of reform.” The government continued to respond to drug addiction, mental health and poverty mostly through law enforcement. The city had yet to turn its attention to juveniles and how to keep them out of the criminal system. “We’ve reduced our prison population, but we haven’t changed our understanding of what people need,” she said. “We haven’t shifted dollars and resources to communities to do more social services than we do criminal services.”

But in the weird alchemy of Philadelphia today, it didn’t seem like a fantasy to imagine those deeper structural changes moving forward. When the city decided earlier this year to allow nonprofits to run supervised-injection sites for drug users, Krasner described the reorienting of power and perception that was taking root in Philly. “What we have today is the celebration of the fact that government is following a movement that is showing them where to go,” he said.

The Eagles beating the Patriots in the Super Bowl in February felt to many in the city as if part of the world they knew had turned magically upside-down. The week after the underdog win, a veteran prosecutor named Chip Junod entered a room in the courthouse where two dozen people had been summoned. They had all been arrested for possessing small amounts of marijuana. Junod is 64, a lifelong Philadelphian, and he started at the district attorney’s office in 1987, with a stopover working as a court-appointed private defense attorney representing indigent clients. Under Krasner, he was made supervisor of diversion programs, and on this day he wore a suit coat over a No. 86 Eagles jersey. Philadelphia is a sports-mad city, its fans celebrating not infrequently by breaking things or climbing light poles greased by workers to impede just such ascents. In the City of Brotherly Love, people seemed to come together less out of some mutual affection for the home team than out of a shared sense of being downtrodden and needing to lash out.

But mutual suffering had also led to Larry Krasner, and to Junod’s delivering a Super Bowl speech to those arrested on drug charges. “I think I said, ‘Not only did the Eagles win, the district attorney is withdrawing all charges,’ ” he told me. Everyone there was free to go home — no diversion program, no fee, no arrest on their record. It was Krasner’s new policy. Most of the people arrested on these low-level offenses, Junod said, had been picked up in the city’s black neighborhoods. In other parts of Philadelphia, people caught smoking weed were issued citations or ignored. But in areas where officers targeted sellers, the police swept up buyers and smokers in their arrests. No more. The roomful of pot smokers remained silent as they gaped at Junod in his Eagles jersey and suit, trying to make sense of this prosecutor who just wanted to send them home.