Former Maryland Gov. Martin O’Malley announced Tuesday that he has leadership teams from 21 states, plus the District of Columbia and Puerto Rico, supporting his Democratic presidential bid.

The groups showcase long lists of supporters, including former mayors who have come out to back the one-time Baltimore mayor. They include former Las Vegas mayor Oscar Goodman, former Pittsburgh Mayor Tom Murphy, and former Miami Mayor Manny Diaz.

RELATED: See the list of who’s on O’Malley’s leadership teams

The list also includes former presidential candidate Gary Hart, whom O’Malley worked for, and former Montana Gov. Brian Scwheitzer, who recently signed on as a national co-chair for the campaign. And it includes six legislators from Puerto Rico, where O’Malley was an early voice on the territory’s debt crisis.

O’Malley has struggled to get out of his low-polling rut, but hopes a winnowed Democratic presidential field — which has been cut in half in the past two weeks — will give him the attention he needs to succeed. And he’s maintained a robust campaign infrastructure that has staff quietly working on the ground in early states and securing endorsements from political leaders.

“Our campaign is proud to have the endorsements of local leaders who, like Governor O’Malley, have a proven track record of getting things done,” said O’Malley campaign manager Dave Hamrick in a statement. “Governor O’Malley is campaigning the old-fashioned way, one living room at a time. Our campaign is not one that is being backed by Washington insiders, but by local influencers on the ground who understand it’s time for a bold, progressive, new leader with a proven ability of getting results.”

Democratic front-runner Hillary Clinton has so far dominated the endorsement race, locking down support from a majority of Democrats in both chambers of Congress, as well in governors’ mansions across the country.

O’Malley has one member of Congress in his camp, California Rep. Eric Swalwell, while Sen. Bernie Sanders, another candidate in the Democratic field, has two congressmen.

The former Maryland governor’s leadership team includes 60 endorsers from Iowa and 25 from New Hampshire, states which hold the first two nominating contests in the Democratic primary. Not surprisingly, he also nabbed a long list of supporters from Maryland, as well as supporters from South Carolina, Nevada, California, Kentucky, Montana, Nebraska, Colorado, Texas, Georgia, Virginia, Ohio, New Jersey, Massachusetts, Pennsylvania, Wisconsin, Arizona, Illinois, Washington, D.C. and Puertro Rico.

See the full list here, as provided to MSNBC by the campaign.