Larry Krasner is a highly atypical district attorney. For one thing, he'd never prosecuted a criminal case before he became Philadelphia's top prosecutor. Instead, he made his name as a defense attorney representing activists from Black Lives Matter and the Occupy movement, filing a whopping 75 civil rights lawsuits against the Philadelphia Police Department.

So when Krasner ran for the Philadelphia DA seat last year, his victory seemed highly unlikely. Philadelphia has the highest per capita incarceration rate among the 10 biggest cities in the U.S., and a deep-rooted, tough-on-crime culture that has informed its justice system for generations.

So when Krasner ran on reversing decades of mass incarceration, his campaign drew scorn, and then fear, from the criminal justice establishment. The president of the local police union initially called his candidacy “hilarious,” and a group of former prosecutors penned a letter calling him a “radical candidate” who was “dangerous to the city.”

Nevertheless, Krasner trounced his opponents in the Democratic primary and then again in the general election, drawing many more voters than any DA’s race in recent memory. His victory remains the most stunning, even as the national criminal justice reform movement focused on dismantling mass incarceration at the local level continues to rack up election wins.

Now Krasner faces the unique challenges of an agitator suddenly handed the instruments of power. So far, he’s continued to shake things up: He revealed that his predecessor kept a secret list of bad cops who weren’t allowed to testify in court, directed his office to stop pursuing low-level marijuana possession cases, and ended the practice of charging cash bail for most minor offenses.

But there will be obstacles as he continues his campaign of reform. When asked whether he expected resistance to his project from people within the system he’s trying to transform, Krasner said, “I think there will be resistance. I don’t worry about it. Because the fact is, these are the people who got us here. We have not always suffered from mass incarceration — it has been the accumulation of their decisions and their power over the last 30 years that caused this problem.”