In the feud — if that’s what it is — between Police Commissioner William Bratton and his predecessor, Raymond Kelly, I’m on Commissioner Kelly’s side. I hope he sticks with the questions he’s raising all the way to the mayoral race of 2017.

Somebody should. I’m not an expert — and don’t have a view one way or another — on the veracity of the crime statistics at the center of their argument. But this strikes me as about more than the fine points of the way murders and shootings are being tallied.

It’s true that it was over the statistics that the long-simmering tension between Messrs. Kelly and Bratton burst into the open this week, after a radio interview Mr. Kelly gave to the president of Teamsters Local 237, Gregory Floyd.

Mr. Kelly suggested skepticism was in order regarding the de Blasio administration’s numbers, which it has touted as proof of a successful year fighting crime. (There have also been reports from John Jay College and the Brennan Center suggesting that, even while murders are up a bit, crime rates have remained low.)

“I think you have to take a look at those numbers,” Mr. Kelly said, adding that he thought there are “some issues with the numbers that are being put out. I think there is some redefinition going on as to what amounts to a shooting.”

“And I can tell you,” Mr. Kelly continued. “People don’t feel safer in the city. People say this to me all the time. And perception is reality in many instances. The city feels unsafe in many people’s minds.”

Mr. Bratton blew up at this. “Shame on him,” he said of Mr. Kelly. He suggested Mr. Kelly was just trying to sell more copies of his memoir, “Vigilance.” That’s silly (memoirs just don’t bring in a lot of money).

Mr. Kelly doubled down Tuesday. He said that “active members” of the New York Police Department have told him that the de Blasio administration “has changed the way shooting victims are calculated.”

He said tallies of shooting victims are now often excluding graze wounds. Ditto a victim wounded by flying glass caused by a shooting. He suggested that wounds of non-cooperative victims have been recorded as self-inflicted.

No doubt Mr. Kelly understands that he is challenging the biggest bet in Mr. de Blasio’s entire mayoralty — the idea that New York can retreat on policing (and intelligence gathering) without jeopardizing safety.

It’s not as if Mr. Kelly threw the first punch. That was thrown by Mr. de Blasio in his mayoral campaign, in which he vowed not to appeal Judge Shira Scheindlin’s finding that the NYPD stop-and-frisk program was bigoted and unconstitutional.

That campaign against the cops was cynical and divisive even by New York City’s standards. The newly elected mayor then dropped the defense of the Finest in the appeals court and allowed the lower-court ruling against the NYPD to stand.

Mr. De Blasio is a left-wing politician who spent his honeymoon in Castro’s Cuba and once welcomed the dictator of Zimbabwe, Robert Mugabe, into City Hall (he now regrets it). What is Commissioner Bratton’s excuse for failing to defend the NYPD?

It would’ve been far better for both of them to have defended the city’s right to use the stop-and-frisk tactics that Mayor Bloomberg and Commissioner Kelly used. They could have done so even while ending the tactics they deem no longer necessary.

The same can be said in respect to the city’s surveillance program in Muslim communities. This is being challenged in court by the same left-wing law firm that brought the stop-and-frisk cases.

Already Messrs. de Blasio and Bratton have ended the demographics unit that was doing such intelligence collecting. Whether they’ll settle the case or defend the NYPD’s practices remains to be seen.

Certainly the logic of such surveillance is being thrown into sharp relief in the wake of the slaughter by Islamist killers in San Bernardino. It’s no small thing that the city didn’t get attacked on the Bloomberg-Kelly watch.

Is all this enough for Mr. Kelly to make a full mayoral campaign? That will require more than vigilance on crime and terror. There are the budget, traffic, regulation and education issues to deal with — and a sense that the city is pricing out its middle class.

What Mr. Kelly knows is that it’ll be hard for the city to advance on anything if it’s not winning against crime and terror. So it was good to see the report in The Post last week that he has given the “go-ahead to supporters to contact potential contributors.”

This column first appeared in the New York Post.