SO SUCCESSFUL and generally well-regarded was Cathy L. Lanier during her nine years as D.C. police chief that anyone selected to succeed her might have a hard time measuring up. It makes sense, then, that Mayor Muriel E. Bowser (D) would turn to someone who worked side by side with Ms. Lanier in transforming the department into a model agency. In tapping longtime veteran Peter J. Newsham as the new chief, Ms. Bowser is betting that past experience will help the District meet the bracing public-safety challenges of today and those of the future.

Ms. Bowser announced Thursday that the 52-year-old Mr. Newsham, acting chief since Ms. Lanier’s departure in September, was her choice to permanently lead the department of nearly 3,800 officers. A 28-year veteran of the D.C. force, he spent 14 years as an assistant chief, working closely with Ms. Lanier and her predecessor, Charles H. Ramsey, as they sought to reform and professionalize a department confronted with high murder rates and plagued by police shootings. Their success is reflected in a declining crime rate, the pioneering use of data and a department held out as a national example of how to make community policing work.

Mr. Newsham must be confirmed by the D.C. Council, and it is clear he will be asked to answer for what some see as blemishes on his record and issues in his personal life. Foremost among these was his involvement in the controversial arrests in Pershing Park during anti-globalization protests in 2002. Hundreds of people were arrested before being given a chance to disperse, and some were hog-tied and held for more than 24 hours. The resulting lawsuits cost the city millions of dollars. Talking to reporters Thursday, Mr. Newsham said he thought at the time his decisions at Pershing Park were “in the best interest of public safety,” but that he had “subsequently determined that was not the right decision.”

That Mr. Newsham lived through the good and bad times of the department and has taken away lessons from both puts him in good stead to deal with the issues that confront the department, including an aging police force and the need to help underserved communities. He also will be aided by the fact that he — much like Ms. Lanier — has made it a priority to be a visible presence in D.C. neighborhoods, visiting crime victims and hearing community concerns.

If there is one thing he wants known about the department, it is that “when you call us, we will always come, and when we come, we are coming to help.” That’s the right goal; we look forward to learning more during his confirmation hearings about what he wants to accomplish and how he will go about it.