Baltimore's persistent poverty and crime have done little to dampen the popularity of the city's charismatic young mayor, Martin O'Malley.

But the mayor's inability to secure firm, reliable leadership for his police department could start to wear on his image, especially if he considers a bid for a statewide office, political analysts say.

Last week, O'Malley's fourth police commissioner in five years, Kevin P. Clark, took a leave from the post while being investigated in the alleged assault of his longtime fiancee.

The mayor's initial choice for the job quit after 57 days. The second, Edward T. Norris, served three years but eventually pleaded guilty to federal corruption charges related to his tenure in the post. The third, a department veteran who became acting commissioner after Norris left, was pushed aside after a month, when O'Malley hired Clark.

Longtime O'Malley supporters believe the mayor can ride out this latest law enforcement dust-up without consequence to his political fortunes -- including a possible run for governor in 2006 -- as long as Baltimore's rate of violent crime continues to drop.

But other political analysts questioned last week whether continued dysfunction at the top of the department -- arguably O'Malley's most important Cabinet post -- will leave the mayor vulnerable to attack about his ability to choose effective leaders.

"Up to this point, I think he's enjoyed a Teflon effect," said Keith Haller, a Potomac-based political consultant. "But I think when you have one problem after another, it starts to do damage."

Matthew Crenson, a political science professor at Johns Hopkins University, said that is especially true because "his flagship issue was crime."

O'Malley's opponents, Crenson said, will "point to a string of four police commissioners [and ask], 'Why can't he get somebody to hold a steady job?' "

At the end of last week, the mayor had only one answer to that question: Police chiefs are people, too.

"It's important to remember that even large organizations are made up of human beings," said Steve Kearney, O'Malley's spokesman. "A few are likely to make a bad decision -- either at work or in their personal lives. That's not to condone it. It's just reality."

Del. Maggie L. McIntosh (D-Baltimore) said the residents of Baltimore have accepted that it would take a certain type of chief to wrestle down the crime rate in their city.

"Right or wrong, the mayor has sought out these aggressive cops who have a record of being streetwise, street smart, tough," McIntosh said. "The kinds of guys who will come into the roughest neighborhoods in Baltimore and clean up 20 or 30 years of drug-infested streets. Guys who run high-risk operations but have had tremendous success."

That was certainly true when O'Malley reached into the upper ranks of the New York Police Department and hired Norris to bring that city's aggressive crime-fighting tactics to Baltimore.

Norris had initial success. The number of homicides declined to 261 in 2000, the first time in a decade that it was below 300. Then, in August 2002, the chief came under scrutiny for his use of an off-the-books expense account to finance thousands of dollars in trips, meals and gifts.

Initially the scandal subsided, and Norris was tapped by Gov. Robert L. Ehrlich Jr. (R) in 2002 to be the Maryland State Police superintendent. But in December, a federal grand jury indicted him on fraud charges related to the expense account. He pleaded guilty in March and faces up to a year in prison.

After Norris, O'Malley brought in Clark, who was executive officer of the narcotics division at the New York department's organized crime control bureau. Clark took a leave of absence last week after he became the subject of an investigation by Howard County police stemming from a May 15 argument with his fiancee. Clark has denied allegations that he assaulted her.

O'Malley's political opponents said the situation, in the context of past problems, could become grist for a serious critique of the mayor.

"The ability to pick good people is a key ingredient of being a good leader," said state Republican Party Chairman John Kane. "I think the result speaks for itself."

Del. Richard S. Madaleno Jr. (D-Montgomery) said the episodes "undermine what should be a strength of O'Malley's, his executive experience." Madaleno, who is closely allied with Montgomery County Executive Douglas M. Duncan (D), said the problem will be amplified if O'Malley and Duncan become political rivals for their party's gubernatorial nomination.

That said, both Duncan and Ehrlich have their own police chief trouble. Ehrlich hired Norris to run the state police before he was indicted and forced to step down. And one of Duncan's chiefs, Charles A. Moose, was reprimanded and eventually resigned over ethical questions about his decision to profit from a memoir largely focused around the Washington area sniper case.

Kearney said he believes the real test for O'Malley should be the results delivered by the police during O'Malley's tenure. "When it comes to judging an administration like ours, people are smart," he said. "They'll see violent crime is down 37 percent in four years. They'll see home values have nearly doubled. They'll see a city that is clearly heading in the right direction."

That may be, said Haller, who is president of Potomac Inc., which conducts public opinion polling, political consulting and market research. But if Baltimore continues to struggle with poverty and crime, and with the management of its police department, that could resonate, too.

"Right now . . . people aren't looking at him as being responsible for these issues," Haller said. "But all that can change."