The overwhelming Democratic primary victory on Tuesday of Larry Krasner, the Philadelphia district attorney whose opponent tried to paint him as soft on crime, represented a major step forward for the growing progressive prosecutorial movement of which Mr. Krasner is a leader, advocates of criminal justice reform said.

With some ballots still to be counted, Mr. Krasner was winning by nearly 50,000 votes out of about 160,000 votes cast, indicating that even with violent crime rising sharply, voters were willing to stick with a candidate who had stopped prosecuting several categories of low-level crime and had pledged to further change the system that he argued locks up too many people for too many minor offenses.

“We hear all this talk about how somehow progressive prosecution can’t survive,” Mr. Krasner said in his victory remarks on Tuesday night. “That’s not what I see. What I see is that traditional prosecution can’t survive.”

As in his first campaign, in which he ran against six other candidates, Mr. Krasner won significant support from Black voters in the northern and western parts of the city. Those neighborhoods have been the most affected by gun violence, and were places where his opponent, Carlos Vega, a former homicide prosecutor fired by Mr. Krasner when he took office in 2018, had hoped to make inroads.

Ben Waxman, a political consultant in Philadelphia and former communications director for Mr. Krasner, said that along with the Black vote, Mr. Krasner had also maintained his support from white progressives.

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In an interview on Wednesday, Mr. Krasner, 60, said elected officials were only a small part of a larger cultural movement for criminal justice reform and reducing incarceration.

“We must recognize that there’s an arc of progress here,” he said. “This election itself is one more very positive sign that what’s happening here is a broad social movement with popular support that’s not going to be reversed based on some cheap politics of fearmongering.”

Mr. Krasner’s decisive victory could help spur on prosecutorial candidates with a similar agenda. They can now argue, with some evidence, that views of criminal justice, at least in diverse urban areas, are unlikely to return to where they were 10 years ago and that the elections and re-elections of prosecutors like Kim Foxx in Chicago and Marilyn Mosby in Baltimore are not aberrations.

Throughout his campaign, Mr. Krasner argued that a 40 percent increase in homicides in Philadelphia last year had nothing to do with his policies, pointing to cities with more traditional prosecutors that had experienced similar trends during the coronavirus pandemic.

Mr. Krasner does not prosecute some low-level offenses, such as drug possession and prostitution, and has sought more lenient sentences than his predecessors.

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Mr. Vega argued throughout his campaign that the leniency of Mr. Krasner’s policies had led to the increase in crime, but criminologists said there would be no way to prove those assertions.

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Mr. Vega received ample support from the police, whose powerful union poured tens of thousands of dollars into his campaign and jabbed at Mr. Krasner as soft on crime at every opportunity.

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