One morning this week, Eric Adams sat down at a sidewalk table outside the Washington Square Diner, in the West Village. Two decades ago, at the end of his career in the N.Y.P.D., Adams had worked nearby, in the Sixth Precinct. “This was my post,” he said. A waiter plopped a stack of thick menus on the table. Adams, who wore a crisp white dress shirt, with cufflinks, credits a strict vegan diet and exercise regimen with reversing a diabetes diagnosis. He ordered a peppermint tea.

Over the years, Adams, who is running for mayor, has cultivated a reputation as someone difficult to pin down politically, particularly on issues of law enforcement. “They can’t put me in a category,” he told me, deploying a favorite line with a smile. “I’m a New Yorker. We’re complex.” Born in Brooklyn and raised in Queens, by a single mother, Adams was beaten by N.Y.P.D. officers in the basement of a South Jamaica precinct house when he was fifteen years old. A few years later, heeding the advice of a mentor, the Reverend Herbert Daughtry, Adams joined the city’s police ranks, hoping to fight racism and abuse from inside the system. In the nineteen-nineties, he came to public prominence as a co-founder of a police reform group called 100 Blacks in Law Enforcement Who Care. The group denounced police killings and abuse, and did community outreach, holding seminars for young Black men on, for instance, how to behave during a stop-and-frisk. “Reaching while black shouldn’t be punishable by death,” Adams told the Times, in 1999. “But I can’t teach kids on the way it ought to be. I have to teach them on the way it is.” In the two-thousands, after retiring from the N.Y.P.D., as a captain, he was elected to office in Brooklyn, first to the New York State Senate and most recently to the post of borough president. Along the way, he made little secret that City Hall was his ultimate goal.

Adams stands between the city and its police department. Once an inside dissenter, he is now an outside advocate. He believes deeply that policing can be a noble profession, and that it is a societal necessity. “That uniform is a symbol of public safety,” he said. He rejects the arguments of police abolitionists, and waves away calls to defund the police. In his campaign for mayor, he has pledged to help the city’s thirty-six thousand police officers do their jobs while betting that he can still attract widespread support among the city’s Black voters—and that bet has paid out, according to the polls, some of which have started showing Adams leading the crowded Democratic Party primary field, with just a month to go in the race. Many voters have also started to tell the pollsters that crime is a top issue for them. That has surprised some, given that New York has spent years enjoying historically low crime rates. But Adams said that it came as no surprise to him. “I don’t care if you live on West Fourth Street or if you live in Brownsville,” he said. “You want to be safe. That is the prerequisite to prosperity.”

His opponents have tried to tag him as a conservative, a corrupt machine pol, a crank. Many critics have made much of the fact that, for a time in the nineteen-nineties, Adams switched parties, a decision that his campaign says grew out of frustration with the Democrats’ record on crime and race. (In the 1999 article about him in the Times, the reporter noted that Adams “calls himself a conservative Republican.”) But Adams doesn’t shrink from the past; in fact, he is perhaps the candidate in the race most interested in talking about it. “If you were to do an analysis of who is in office, and who is running for office, they don’t remember the old New York,” Adams said. “They know the New York. But, see, many of us, we know the old New York. That is why you see this trepidation, this anxiety, because we fought so hard to get out of that time.”

One of the key figures in Adams’s old New York is Jack Maple, a former N.Y.P.D. official who, in the nineties, helped usher in a new era of policing in the city. If Daughtry, a reverend, convinced Adams to become a cop, it was Maple who instilled in Adams the faith in policing that he still holds. “I’m glad I knew him,” Adams said. “He changed my life.”

If you look Maple up on Wikipedia, you’ll see a black-and-white photograph of a portly, jowly white man wearing a bow tie and a homburg hat. If not for a splash of graffiti visible on a subway door behind him, the photograph could be confused for one taken in the nineteen-forties. “He was a real New York character,” Adams said. In his later years, Maple—who died in 2001, at the age of forty-eight—was a tabloid fixture, known for dining out at Elaine’s and talking big and smoking big cigars. But he had started out as a “cave cop,” patrolling subway platforms. In the eighties, he ran decoy squads—cops playing stock characters such as “the Jewish lawyer,” “the blind man,” or “the casual couple”—to catch muggers in the caves. He then started creating hand-drawn maps of the subway system, which he dubbed the “Charts of the Future,” trying to predict where crime would occur next and come up with tactics to stop it. “This is a revolution,” he would later tell The New Yorker. “Remember how Hannibal used infantry and artillery together, or how Napoleon used rapid deployment? Those were revolutions, and so is what we’re doing.”

In 1990, when William Bratton was installed as the head of the Transit Police, he discovered Maple’s work, and promoted him to be his special assistant. By 1992, robberies in the subway system fell by a third. Adams, who also started his career in the Transit Police, had a front-row seat to the Maple and Bratton show. As a student at the New York City College of Technology, he had learned some early programming languages—COBOL, Fortran—and, in the Transit Police’s data-processing center, he was in charge of compiling a monthly crime report. Maple started coming by his desk. “I remember it like it was yesterday,” Adams said. “His sitting down and looking over the reports, and he was, like, ‘Eric, you see this?’ ” Maple started making predictions about what would be on the following month’s report, and Adams was dazzled to see that Maple’s predictions would often come true. “He was just a smart guy when it came down to crime,” Adams said. “He had a knack for patterns.”

It was Maple’s contention that police needed to be collecting and distributing crime data much more often, and reacting to it much more quickly. In 1994, when Mayor Rudy Giuliani picked Bratton to be the police commissioner, Bratton named Maple his deputy commissioner and chief strategist. Together, Bratton and Maple created CompStat, a data-focussed approach to policing that was credited with helping to transform New York into the safest big city in the country. CompStat was eventually adopted by police departments around the world. Adams was part of a team that helped put together the early versions. “I was just this computer geek,” he said. “We were building out the first layers of this new form of thinking. We had no idea we were going to make this impact. Trust me, it was unbelievable.”

Adams was a decade into his law-enforcement career when he met Maple, and during those years the city’s murder rate had peaked to historic levels. “Remember, pre-Jack, no one in this country believed that police had anything to do with making cities safe,” Adams said. “Everyone said it was social conditions.” Bratton and Maple, he said, had made a compelling case for police playing a role in crime reduction—but Giuliani, he added, had run Bratton out of town before he could implement the second part of the program. Adams said that this next phase was to be crime “prevention,” and was supposed to follow the “intervention” tactics of the early CompStat years. He tented his fingers together in front of his face, and narrowed his eyes. Giuliani, he said, had got “addicted” to intervention, which produced statistics that played well politically. “I saw Giuliani take the methodology and abuse it,” he said. “Giuliani instilled generational trauma and anger and fear.”