O'Malley's administration reached its lowest homicide figure of 253 in 2003, before the number rose to 276 during his last year in office before becoming governor.

Former Mayor Sheila Dixon and Rawlings-Blake each embraced a policy of targeted arrests, and the arrest rate dropped, along with the murder rate. Former Police Commissioner Frederick H. Bealefeld III — who led the department under Dixon and Rawlings-Blake — often preached about "fishing with a spear instead of a net."

During Rawlings-Blake's tenure as mayor, homicides reached a low of 197 in 2011, but rose last year to 217.

In meetings with criminal justice leaders in recent weeks, O'Malley has advocated for more arrests. The governor's reasserting himself about city policing sparked disagreement from candidates vying to succeed him, first by Gansler.

"Let's not use empty talk about mass arrests in Baltimore as a substitute to doing the hard work to make this city safer for everyone, in every neighborhood," Gansler said, as he announced his candidacy in the city's Reservoir Hill neighborhood on Tuesday.

Del. Heather Mizeur of Montgomery County, another Democratic candidate for governor, said Wednesday that "community building" is more important than arrest rates.

"The solution is not as simple as racking up more arrests so we can pat ourselves on the back with crime-fighting statistics," she said.

O'Malley's policies got the city into legal trouble. During the Dixon era, the city paid $870,000 to settle a civil rights lawsuit filed by the American Civil Liberties Union and the National Association for the Advancement of Colored People, who alleged a broad pattern of abuse in which thousands of people were detained without probable cause. That settlement led to the appointment of an auditor to review the city's so-called "quality of life" arrests for minor nuisance crimes.

At the time, O'Malley said the settlement was not a rejection of his policies, but rather a legal strategy to bring an end to litigation.

O'Malley's call for increased arrests found mild support from one Republican candidate for governor, but two others lampooned the idea.

Del. Ron George of Anne Arundel County said stepped-up arrests could help — but not if the prison system fails to rehabilitate inmates. "They just get worse," he said. "What they learn about, they're worse when they come out."

Craig, of Harford County, called O'Malley's proposal "ludicrous." He said: "They need to fix the corrections system itself before saying anything further about arresting more people."

Republican Charles Lollar, a Charles County businessman who's also running, called it "comical" that O'Malley would criticize the city he once led, saying that high unemployment and the governor's economic policies contribute to the rising violence.

"Rawlings-Blake has inherited a mess that the governor should be ashamed of himself over," Lollar said. "It's typical of this administration, because they've always been about fluff. He wants to be elected president, and he's going to even step on his own supporters to get there."

In the opinion piece, O'Malley said during his tenure as Baltimore's mayor the city had "the largest reduction in total crime and property crime and the second-largest reduction in violent crime … of the 20 largest cities in the country."

State Del. Jill Carter, a Baltimore City Democrat, was one of the first to raise concerns about the high arrest rates under O'Malley. Carter said she was "vilified and demonized" for speaking out.

"People were getting harmed," she said Wednesday. "People lost their jobs and their homes. It destroyed the spirit of whole communities. Police were wasting time and effort on nonserious matters, and some serious crime really went unaddressed. It created a rift between the police and the community. There was no trust."

Baltimore Sun reporters Michael Dresser and Erica L. Green contributed to this article.