The abrupt retirement of New Orleans Police Superintendent Ronal Serpas created a void that Mayor Mitch Landrieu quickly filled Monday with the swearing-in of Lt. Michael S. Harrison, an officer of 23 years tapped to lead the Police Department on a temporary basis during the search for the city’s next police chief.

But in the wake of Serpas’ departure, there were early indications that Harrison, a low-profile commander who most recently headed the department’s 7th District in New Orleans East, could soon be shedding the “interim” qualifier from his shiny new title of superintendent.

Praising Harrison’s “exemplary leadership,” Landrieu stopped short of calling the New Orleans native a shoo-in for the permanent post. But the mayor said conspicuously little about the hunt for Serpas’ successor and suggested the job was Harrison’s to lose.

“I would say that possession is nine-tenths of the law,” Landrieu said at a news conference at City Hall, mentioning no plans for a national search for a new top cop. “I would not have promoted Cmdr. Harrison to this position if I did not think that he could lead the department.”

The mayor, who is tasked with appointing the police chief, said he hoped to gain community input at a series of upcoming meetings. Harrison has “all of the qualifications that are necessary,” Landrieu said, “but I want to hear from the public about what it is that they want and what it is that they need. I will decide in the relatively near future about who the permanent person is going to be.”

Harrison, 45, who took the oath moments after Serpas announced his retirement, said he was “extremely humbled” by the opportunity — a promotion that nearly doubled his annual salary to $150,000.

“I believe policing is one of the most noble professions ever,” Harrison said. “We are on the front lines every day with incredible responsibilities and rewards, and, after serving for 23 years, I’m clear that when I put this uniform on every day, my highest mission is to serve and protect. I stand ready to lead this department through its next chapter.”

“We must continue to improve the quality of life by working for and with the community,” he added, promising to “have my ear to the ground listening to your feedback and looking for opportunities to build stronger relationships across the city.”

Harrison’s background differs sharply from that of Serpas, who holds a Ph.D. and led the Washington State Patrol and Metropolitan Nashville Police Department before taking the helm in New Orleans in 2010. Some observers questioned whether Harrison, 45, has enough experience to steer the NOPD through the challenge of implementing a federal consent decree that mandates sweeping changes within the long-troubled department.

Peter Scharf, a criminologist at Tulane University who follows the NOPD, described Harrison as a “competent lieutenant with a B.A. degree but very little senior management.”

“Michael seems like a very nice guy,” he said, “but his experience is really operational and supervisory. People wondered why he’d been promoted to commander in 2011. Not to disparage Michael at all, but I’m not sure he had the pedigree of someone you’d promote to the position of lieutenant.”

Raymond Burkart III, a former attorney for the local Fraternal Order of Police lodge, called Harrison’s promotion to the top spot an “unconscionable” gesture of disrespect to officers who believe in earning their way through the ranks. At least two dozen NOPD officers outrank Harrison.

“I find it completely dishonorable and a slap in the face to higher-ranking officers, including current and former deputy chiefs, to promote a lieutenant to superintendent of police,” said Burkart, whose father is a major in the Police Department.

“It’s another shotgun blast to morale, which already is paper-thin and hanging by shreds,” Burkart added, saying he’d heard from rank-and-file officers throughout the day who called or texted to register their discontent.

Kirk Bouyelas, a former deputy superintendent now working for the District Attorney’s Office, acknowledged Harrison’s move from commander to interim chief is a leap. “I’m not going to sugarcoat it,” he said.

But Bouyelas disputed the notion that his former colleague is unprepared for his new role, saying Harrison gained invaluable experience overseeing operations in the huge 7th District.

He described that assignment as “almost like being police chief of your own small city.”

“The bottom line is he’s up to it,” Bouyelas said. “If he does the right things and is thoughtful, I really do believe the rank and file will respond to that in a positive way. The best thing the organization can do is give Mike an opportunity.”

Landrieu beamed as he described Harrison’s attributes. He said the sudden switch at the top of the department “actually falls beautifully into the strategy to begin to develop the city for a new generation of leadership, and I believe that, at this time, Cmdr. Harrison represents what that looks like.”

He called Harrison “a man of great integrity” and said: “He is a man of discipline, hard work, focus, and his relationship with the community is spectacular. I expect that he will be able to lead this department exceedingly well.”

A 1987 graduate of McDonogh No. 35 High School, Harrison ascended the NOPD’s ranks swiftly after joining the force in 1991. He was named a detective in the major case narcotics section in 1995, a sergeant in the 8th District four years later, then a supervisor in the Public Integrity Bureau in 2000.

By 2009, he had been named assistant commander in the 7th District, which encompasses the vast bulk of New Orleans East.

He served as commander of the Special Investigations Division from January 2011 to 2012, managing the NOPD’s criminal intelligence, narcotics, vice and gang enforcement units. He later was promoted to district commander, a position that earned him $78,000 a year.

“He’s kind of been flying below the radar out there in New Orleans East for the past few years,” said Donovan Livaccari, a Fraternal Order of Police spokesman. “My refrain for today has been, ‘Superintendents come and go.’ I’m sure there will be things we disagree with Mike Harrison on, but we’ll try to make things as good as we can for the officers and the citizens of the city.”

Harrison, an Algiers resident whose wife stood at his side during Monday’s news conference, is also a minister at The City of Love church. “The single most important reason why I’m here today is because God has blessed me and smiled on me,” he said.

City Councilman James Gray, whose council district includes most of New Orleans East, said he’s impressed with the new interim chief. Gray said Harrison has been responsive to concerns and has the respect of officers.

“I hope he ends up being the permanent chief,” Gray said. “The mayor suggested to us that he has looked at home and got what he thinks is the best available (candidate). He thinks (Harrison) is going to be the guy. That’s the sense I have in talking to the mayor.”

Harrison doesn’t come with an unmarred record as an officer. In 2011, he was suspended for one day for improperly disposing of NOPD uniform shirts after a resident reported finding them in the garbage bin of a Terrytown car wash. An internal investigation, conducted by Bouyelas, found he had violated departmental policy by throwing out old uniform shirts with the patches still attached. According to his civil service file, he also was reprimanded in 2002 and 2004 for being involved in “preventable” traffic crashes.

Also in 2011, Harrison was sued by former Sgt. Ronald Ruiz, a former detective who claimed Harrison and other PIB officers illegally pulled him over and questioned him in Jefferson Parish. News accounts at the time said investigators had been probing whether Ruiz filed a false workers’ compensation claim. Ruiz, however, has said he was ambushed and felt intimidated during the traffic stop, during which Harrison persuaded him to sign a letter of resignation.

Rafael Goyeneche, president of the Metropolitan Crime Commission, a watchdog organization, said he believes Harrison is likely to be the long-term chief for several reasons, among them that Landrieu is a “lame-duck mayor.”

“If you are a police chief in another city, are you going to come here knowing that you might only have the job for a couple of years?” Goyeneche said. “That’s compounded by the fact that there is a critical shortage of police officers, plus you’re dealing with the implications of the consent decree that are still being worked through. I don’t know how New Orleans stacks up as an attractive position for outside police chiefs, so I think Chief Harrison might very well be the long-term choice.”

Goyeneche praised Harrison as “a local guy who bleeds blue,” but he cautioned that a change in leadership will not cure many — or perhaps any — of the department’s woes overnight, including a 36-year low in manpower, the rigors of the consent decree “and some attendant morale issues.”

“There’s a lot the chief doesn’t control,” he said, and Harrison “has to be able to make lemonade out of some of the lemons he’s been dealt.”

At Monday’s news conference, the new chief’s old boss — whom Harrison described as “a coach, a teacher, a mentor, a friend” — offered a few parting words of advice. Serpas told Harrison to “be true, stay focused, don’t get distracted by the sideshow barkers, do your job, protect your people and protect your employees.” There will be some pushback to reforming the department, Serpas warned, but Harrison will have to overcome it.

“We have to be a constitutional Police Department, and to uproot and change some of the long-term practices will meet resistance,” Serpas said. “It will be disguised as a morale issue, but, in some ways, it’s just resistance to change.”

Staff writers John Simerman, Gordon Russell, and Martha Carr contributed to this report. Follow Jim Mustian on Twitter, @JimMustian.