STATEN ISLAND, N.Y. – “Criminal justice reform” is a big part of the Democratic Party agenda, both in New York and across the country. You’ll hear the party candidates for president talking about it a lot from now until Nov. 3, 2020.

Progressives have already made inroads by grabbing major law enforcement slots in the Empire State. The revolution is already underway here, and could be a model for the party across the country.

Tiffany Cabán’s all-but-official victory in the Democratic primary for the Queens district attorney’s office is just the latest example.

This is more than just a political blow against the Queens Democratic machine, which had already taken a major hit when now-Rep. Alexandria Ocasio-Cortez (a Cabán ally) took Queens party boss Joe Crowley’s congressional seat out from under him.

If she indeed takes the D.A.'s seat, Cabán’s victory would put progressive criminal justice reform into overdrive, and the effects could spill far beyond Queens.

For years, the Republican Party has focused on the judiciary as their avenue to long-term impact. Put right-minded judges on the Supreme Court or on top federal, state and local courts, and their influence could be felt for decades, circumventing or striking down the work of legislatures.

Progressives have clearly learned the lesson. Instead of marching against the NYPD, or becoming pro-reform elected officials, public interest attorneys or community organizers, they’re targeting the law-enforcement offices themselves. It’s smart politics.

District attorneys have tremendous leeway in setting their offices’ agendas. They can seek indictments. Or not. They can focus on certain categories of crimes, be it drug dealing, domestic violence or drunken driving. Or not. They can target street crime. Bad landlords. Or the police. Wherever they think a wrong needs to be righted.

They can do criminal justice. And they can do social justice. It’s a pretty wide palate.

Cabán ran on a platform of wiping out cash bail, zeroing out prison populations, and a refusal to prosecute low-level offenses like fare-beating and resisting arrest. All in keeping with the vibe of standing down on certain categories of crime that we’ve seen in New York City over the last few years.

Most shockingly, Cabán has said she would not prosecute sex workers or their customers. Which should turn Queens into the biggest sex tourism spot in North America. Sex traffickers are surely rejoicing. The women who do the actual dirty work, including those who are underage? Not so much. There’s nothing empowering about prostitution. This isn’t “Pretty Woman” we’re talking about.

Cabán isn’t alone. Attorney General Letitia James has the top law-enforcement slot in the state, and has already put a progressive agenda into action. She’s made it her mission to oppose President Donald Trump, saying her office would not cooperate with Trump’s anti-immigration efforts. She wants Trump’s tax returns released. She’s looking into Trump’s business dealings.

She also wants past pot arrest records expunged if weed is made legal for recreational use in New York. She gave key legal backing to New York giving driver’s licenses to illegal immigrants.

Criminal justice or social justice? Depends on which side of the aisle you’re on.

Everyone wants a fair criminal justice system. But outright refusing to prosecute certain crimes, or declining to prosecute offenders who are a certain demographic, isn’t “fair.” It can be dangerous. It sends the message that committing a crime is OK. It’s the definition of a slippery slope, because if we let one crime go unpunished, it’s easier to let other crimes follow suit. Police will be quick to get the message about the collars that they should and shouldn’t make.

But where do crime victims go for justice if the system is tilted in favor of those who commit the offenses, if some crimes are simply overlooked? If offenders needn’t fear the long arm of the law? If the threat of jail is removed from the equation?

Queens might be on its way to finding out.