The appointment of William Bratton as the next chief of Police at Los Angeles will, if it is approved by that city’s weak legislative branch, finally settle one of the important debates in policing. Ironically, it has been the liberals who have for years been denigrating the power of government to influence crime rates, which they have held are fundamentally demographic phenomena, while conservatives have argued for expanded and assertive policing. That is, after all, a stepped up role for the state.

In the late 1980s and early 1990s, crime was at record levels in New York and cities around the nation. Liberals insisted that policing could accomplish little if anything. Hard-line conservatives advocated get-tough policies as the only solution. Donald Trump actually took out full-page ads in New York papers advocating the restoration of the death penalty, as well its liberal usage, in the aftermath of 1989’s infamous Central Park wilding case.

When crime rates dropped, evidently as a result of the policies of Mr. Bratton, liberals insisted that this too was the result of demographic shifts, an argument scarcely supported by evidence, especially since as time has passed crime rates have stayed down, but which gained credibility through repetition. Liberals’ other complaint — that Mr. Bratton’s policing style created a more brutal force — has also failed to achieve any evidentiary validation.

During his tenure at New York, Mr. Bratton showed that policing needed to be not tougher and meaner but smarter and more effective. This was a rebuff to L.A. and its drag net style of policing, which, until the accession of New York, had been the dominant American method of policing. Mr. Bratton replicated the success he had already experienced while heading the Boston Police Department and the New York City Transit Police, then a separate department, by focusing on smaller crimes and quality of life violations — many of which proved to be the work of felonious criminals.

By employing the “broken windows” theory of George Kelling and James Q. Wilson in conjunction with the Compstat system, which tracks major and minor crimes block by block and day by day, he managed to halve the city’s murder rate while cutting overall crime by a third in his 27 months of service before leaving due to a clash of oversize egos with Mr. Giuliani. As Mr. Bratton put it during his stint here, “It’s not the economy, demographics, or the weather. We are a results-oriented organization.”

Mr. Bratton’s New York model of policing has won the argument. Thirty percent of police departments now hew closely to the Compstat model, and many others approximate it. Jerry “Spaceship Earth” Brown was elected mayor of Oakland on a positively Rudy-esque crime platform. And now L.A., which has long resisted New York style policing, has appointed Mr. Bratton to lead its force. Mr. Bratton will face new challenges — in a city of 3.5 million that covers an area 50% larger than Gotham, he will command a force less than 25% the size of our own, and more than 1,000 officers short of authorized strength. The crime rate is on the rise, and the police department is internally dispirited and is distrusted by much of the city. If any man can turn this department around, it is Mr. Bratton.