MANCHESTER, N.H. — Maryland Gov. Martin O'Malley has played presidential politics in New Hampshire before. He was here in the Granite State, home to the country's first primary race, just last year as a surrogate for President Obama and Gov. Maggie Hassan. He was here six years ago, stumping twice for Hillary Clinton. And he was here at the start of his career, in 1984, crisscrossing the state and sleeping on floors as a young operative on the Gary Hart campaign.

On Saturday night, at the New Hampshire Democratic Party's annual dinner, a table of old Hart hands looked on as their friend — the college kid on the campaign who made himself a city councilman, then a mayor, then a governor — came back to the state again. But this time, and for the first time, O'Malley was in New Hampshire to talk about himself.

In his keynote speech at the Jefferson-Jackson Dinner, a fundraiser and frequently a venue for national Democratic talent, O'Malley made an aggressive and at times impassioned case for executive leadership, framing his approach as mayor of Baltimore, and the "Believe" campaign he launched there more than 10 years ago, as a strategy that should be applied at the national level.

"The people of Baltimore rallied," he said to a crowd of 1,000 in Manchester's Radisson Expo Center. "Belief is important. Belief drives action. Now, like Baltimore in 1999, we, as Americans, are going through a cynical time of disbelief — a time, quite frankly, with a lot more excuses and ideology than cooperation or action."

"We seem to have lost the shared conviction we once had," O'Malley said, "that we actually have the ability to make things better together."

O'Malley, a possible candidate in the 2016 presidential race, launched the $2.1 million "Believe" campaign in 2002, his second full year in office, to combat the city's twin scourges, drugs and crime. The new mayor blanketed the city in jarring television ads that promoted a hotline, "1-800-BELIEVE," for mentorship and drug treatment programs. The seven-letter slogan — printed in all capitals, a white san-serif font on a background of black — appeared across Baltimore on bumper stickers and garbage cans, buildings and bridges.

"It wasn't about the bumper stickers, or the signs," O'Malley said Saturday. "It was about something deeper: the belief we shared that in our city there is no such thing as a spare American. We continued to act on that belief, and over the next 10 years, Baltimore actually went on to achieve the biggest reduction in crime of any major city in America," he said to applause in the Expo Center.

Before O'Malley took the dais, he was introduced by a three-minute glossy black-and-white video — titled "Belief" — that described the Baltimore campaign and highlighted "CitiStat," the data-driven software he created to track crime. "Things that get measured are things that get done," the narrator says, as images flash by of a young and dark-haired O'Malley touring crime scenes and walking city streets.

The video, produced by Jimmy Siegel, Eliot Spitzer's longtime ad man, looked like a campaign spot, just as easily as O'Malley's talk sounded like the platform of a national campaign in the making. The speech, focusing almost exclusively on Baltimore, was a major departure from O'Malley's previous political appearances.