You’ve heard the old saw about how a good prosecutor can get a grand jury to indict a ham sandwich. It’s a New York special, spoken by a former state chief judge, a joke about the weakness of grand juries and also the implicit nature of hard-charging prosecutors.

But times have changed in Brooklyn, where all six candidates vying loudly for the district attorney’s seat tend to shout “reform” more than “convict.”

The other surprising feature of this race: None of the candidates are longshot outsiders. Five of the six previously worked in the office they’re now hell-bent on reforming, and the sixth worked as a prosecutor in Queens.

How did we get to the point where candidates for the borough’s top law enforcement job are arguing not about whether low-level marijuana crimes should ever be excused, but whether they should be prosecuted?

In this election, the emphasis isn’t on how many murderers the candidates have put away, but how many criminals they’ve diverted from prison.

What’s going on in Brooklyn, and what can we glean from Tuesday’s election results?

How Brooklyn became a nexus for criminal justice reform

The answer to that goes back a couple decades to long-serving district attorney Charles “Joe” Hynes, who took office in 1990.

Hynes developed a reputation as a reformer with programs providing alternatives to incarceration.

But his standing took a hit after allegations of bad convictions and political favoritism to some Brooklyn communities. In 2013, he lost his seat to Ken Thompson, who had new plans for reform.

Thompson rode the beginning of a national wave of criminal justice reform in an era of historically low crime. He led that wave in some areas, establishing a conviction review unit that found more than 20 bad convictions and famously made Brooklyn the first borough to avoid prosecution in many low-level marijuana cases.

When Thompson died in 2016, his chief assistant, Eric Gonzalez, became the acting distict attorney, beginning the race for the next D.A. earlier than expected (Thompson had been set to remain in his position, friendly to incumbents, for more or less as long as he wanted it).

“In the past, prosecutors have always touted their tough-on-crime approach,” says Gonzalez. In his view, given the steadily low crime numbers which have remained where they are under his oversight, his opponents had only one path to victory: “They chose to run to my left.”

Gonzalez says a major part of his job is to “make sure that the community’s actually safe,” a focus instilled in him by a childhood in East New York where he sometimes “lacked a sense of safety and security.”

Still, he calls himself a “progressive,” given his position as a key Thompson deputy who has continued Thompson’s reform policies.

Most of his opponents, naturally, say they would go further, and point to their own formidable backgrounds. Anne Swern oversaw drug-treatment programs and other alternatives to incarceration under Hynes in the 1990s and also worked for the Brooklyn Defenders. Marc Fliedner successfully prosecuted the case against Peter Liang, the former NYPD officer who fatally shot Akai Gurley in 2014. Ama Dwimoh, a former prosecutor in the office, says she would establish an independent commission to further review prosecutorial misconduct. Patricia Gatling touts her own experience in the reforming Brooklyn office and as head of the NYC Commission on Human Rights; term-limited City Council member Vincent Gentile did his prosecutorial work in Queens but also talks approvingly about the hometown history of alternative sentencing and diversion.

What happens next?

Reform-minded progressive criminal justice leadership no matter who wins on Tuesday?

Perhaps. But the reformer’s path is long and slow, as is clear from the decades of work behind each of the candidates.

There’s still progress to be made on one of Thompson’s marquee issues, the slashing of marijuana prosecutions.

A WNYC investigation this week found that around 90 percent of marijuana-possession arrests were prosecuted in 2010. After Thompson took office, that fell to 78 percent in 2014 and around 82 percent in 2016, according to Division of Criminal Justice Services data — not as drastic a drop as the policy’s rave reviews might imply. Those numbers include arrests for smoking in public, which aren’t dropped in Brooklyn.

Gonzalez says that rate is lower than in other boroughs, and that the sheer number of arrests has decreased since pre-Thompson days. But racial disparities in the numbers continue.

Whoever wins on Tuesday will have to juggle reform efforts like these with continually good crime prevention work, which lets reform take center stage. Reformers have often argued that smart changes can let a D.A.’s office focus resources on the serious crimes, which perhaps can happen in Brooklyn. And though it may seem strange to count on some restraint from the officials charged with doing the charging, Thompson’s experience shows that change within is possible. And, judging by the candidates flocking to embrace his approach, popular.