On Tuesday, Philadelphians elected Larry Krasner to be their district attorney. Krasner, a longtime civil-rights lawyer and critic of mass incarceration, has been a frequent litigant against abusive cops and boasts a list of rabble-rousing clientele including activists from Black Lives Matter and Occupy Philly. He was propelled into office by an energized left coalition led by youth and people of color. Their organizing work boosted turnout by at least 69 percent compared with the city’s last DA’s race.

Even as President Trump fulminates against immigrant gangsters and Attorney General Sessions endeavors to reinvigorate the failed “war on crime,” voters have elected a candidate who has said he wants to “end the era of mass incarceration.” It’s an enormous task. Since the 1970s, American policing and prisons have metastasized: At the end of 1980 state prisons held 304,844 people, but by the end of 2015 they held more than 1,330,000. The country’s entire system of cages, which includes everything from federal prisons to immigrant-detention centers, incarcerates more than 2.3 million. Incarceration rates began to decline in 2010, but reducing prison populations to levels comparable to, say, those of Western Europe, will require big changes. The policing and prosecuting practices that filled our prisons are deeply ingrained in the day-to-day practices of the criminal-justice system.

One path forward has been presented by the Coalition for a Just District Attorney, comprising nearly 30 local groups, in their just-released “Vision Of Transformative Policies” for Krasner’s first 100 Days. Their agenda includes ending civil-asset forfeiture, a shameful program allowing police to seize people’s property before they were convicted of a crime (Krasner’s Republican opponent had overseen this program during her time in the DA’s office). It also demands that Krasner decline to prosecute many “quality of life” offenses, from drug possession to prostitution; bring the office’s moribund Conviction Review Unit to life so that it keeps the wrongfully convicted out of prison; take into account whether filing certain charges would increase an immigrant’s risk of deportation; cease to deal with police officers with track records of misconduct; and adopt an open-file system for pretrial discovery, so that defense lawyers have immediate access to the information that prosecutors will use against their clients.

Krasner has not yet issued a full response to this lengthy list of proposals. But he ran on a pledge to divert low-level offenses from the criminal-justice system, crack down on prosecutor complicity with police misconduct, and right wrongful convictions. It won’t all, of course, be easy. He must confront possible resistance from DA office veterans, whom he can fire, and from cops, whom he cannot (though he can and should prosecute them, of course, if they break the law).

Krasner has also pledged to stop seeking the death penalty. That’s a good thing. But Pennsylvania has executed only three people since 1962. The best thing about formally ending the death penalty is that it will allow us to stop talking about the death penalty and focus on the drivers of mass incarceration.

Krasner wants to end cash bail, one essential step in decreasing the number of people behind bars. Cash bail is a patently unjust system that keeps people in jail pending trial based on whether or not they have sufficient financial resources, rather than on whether they might pose a threat to public safety or a flight risk. Reducing the number of people held on bail will help. Roughly 25 percent of those held in city jails, known as the Philadelphia Prison System, are held on bail pending trial, according to the city. Formally ending cash bail won’t be easy, because doing so would require the cooperation of Pennsylvania’s Republican-controlled state legislature. But Krasner believes that he can work toward putting an end to the system in effect by directing prosecutors to request that magistrates release anyone who should not be detained on their own recognizance, and requesting astronomical bail for people if they should. That too, however, will require the cooperation of the Philadelphia court system.

Philadelphia has already made some progress toward reducing incarceration, collaborating with the MacArthur Foundation to reduce the city-jail population by 34 percent. The current city-jail population is roughly 6,729, a 17 percent decrease from the 8,082 locked up in July 2015. A deep reduction in Pennsylvania’s incarcerated population will require that fewer people be held on cash bail. Reducing it further than that will require digging yet deeper. Many held in city jails are there because of technical parole and probation violations. Many of them could be kept out of the system in the first place. But that will likely require the cooperation of the city courts as well. What’s more, roughly one in five in city jails are serving short sentences of 23 months or less. Arguably, many of those sentenced to such short stints behind bars don’t need to be there in the first place.

What’s more daunting, perhaps, is that 13,576 people from Philadelphia were locked up in state prisons as of the end of 2016—thanks to a gargantuan system that cages city residents in far-flung facilities as far as a full-day’s car ride, or an overnight bus-trip, from the city—with 1,694 newly sent from city courts, and another 1,844 for parole violations, last year alone. New Philadelphia court commitments to state prisons declined by 11.4-percent between 2015 and 2016. But bringing those numbers down more dramatically will require reforms beyond ceasing to prosecute small-time quality-of-life offenses.

Prison populations are governed by a simple equation: how many people are sent to prison, multiplied by how many years and months they are sentenced to serve. According to the state Department of Corrections, that number sent to state prison in 2016 included 303 for drug crimes, 270 for robbery, 138 for murder, 289 for aggravated assault, and 293 on weapons offenses. Reducing Philadelphia’s contribution to mass incarceration thus will require the justice system’s not only declining to send some to prison in the first but also sentencing those who are sent away to prison to less time.

“This notion that people are either all bad or all good is untrue, and these changes in criminal justice are going to demonstrate that,” says Krasner. “And there’s going to be a more balanced and reasonable view of what you do with people in cases that we all view as non-serious, and even what you do in cases that are a little bit more serious but appear to be situational, age-related, related to prior trauma, things of that sort, which make it clear that people are not permanently that way.”

Krasner, however, said that “no one seems to be really pushing the idea of getting back to the 1970s levels.” I asked him what it would take to do start having that conversation.

“We can think about it,” Krasner responded. “But we also have to deal with political realities.” If early reductions go well “then I think everybody will be much more open.” But if the typical sensationalist narratives about crime prevail, a “stupid narrative about how one bad result negates all the good results…it will be very difficult to have the buy-in.”

Krasner will likely fall short of the expectations set by the activists who propelled him into office—at the end of the day, his job will involve sending people to prison, while many activists would like to see the prison system destroyed altogether. Both Krasner and his supporters agree that dialogue will be key. Sheila Quintana, a community organizer for the New Sanctuary Movement of Philadelphia, a member of the coalition, says that they are ready to fight for Krasner. And also to fight for their agenda. To make sure that Krasner follows through, they want data on all cases to be made fully public, and quarterly meetings to evaluate progress. “We want a collaborative relationship,” says Quintana. “We know that Krasner’s going to have a difficult time coming into the prosecutor’s office…. we want to support him so that we can actually accomplish the things that we need accomplished…but, of course, continuing to push when necessary for the changes to happen.”