First the firefighters. Now the sanitation workers.

Philadelphia's largest municipal union, representing 9,900 blue-collar employees working without a contract since July 2009, enthusiastically endorsed T. Milton Street Sr. for mayor Tuesday night over Michael Nutter.

"It's a vote of confidence in my ability," Street said at the Walnut Street headquarters of District Council 33 of the American Federation of State, County, and Municipal Employees, whose members include trash haulers and workers from the city's water, recreation, health, and fleet departments.

Street addressed a gathering of the union's 250 delegates before he was overwhelmingly backed in a voice vote, DC 33 president Herman "Pete" Matthews said.

"They obviously were impressed with what he said," Matthews said.

"I don't feel the mayor has supported us, and my membership doesn't feel the mayor has supported us - especially in light of all the money we have saved the mayor over the years," Matthews said.

Nutter was not invited to the gathering. Matthews said Nutter did not ask for the union's endorsement; Street did.

That makes two municipal unions behind Street, who was recently released from federal custody after serving 26 months on three misdemeanor counts of failure to file a tax return, and adds intrigue to what was supposed to be a cakewalk for Nutter.

The 2,100-member city firefighters union announced Thursday it was lining up behind Street, largely in response to the mayor's 2009 decision to deactivate seven companies and appeal a new arbitration award that included a 9 percent raise over four years and exempted firefighters from furloughs.

Both Matthews' union and District Council 47, the city's white-collar union, have been working without a contract for nearly two years.

Street has been invited to address District Council 47 when it meets April 26 to endorse a candidate.

The fourth city union, Lodge 5 of the Fraternal Order of Police, also will not back Nutter for a second term - although it is not backing Street, either.

Nutter would not be endorsed because he wants to eliminate the controversial DROP pension program, whose participants include many officers, FOP president John McNesby said.

Three weeks ago, Nutter's labor-relations officials met with Matthews and his union representatives in the first formal bargaining session held since 2009. The sides did not come any closer to reaching a deal.

In the interim, Matthews maintains, his members - who have not received wage increases or more city aid to cover growing health-care costs - have saved the city nearly $160 million.

Matthews dismissed the questions raised by the choice of a candidate who spent time in prison on the tax counts.

"I agree with what the firefighters said - it is criminal what the mayor is doing to us," Matthews said. He added: "Everybody deserves a second chance. I think even the mayor would say that."

Nutter's campaign spokeswoman, Sheila Simmons, called Matthews' position "hypocritical," given that Nutter had closed a six-year deficit of $2.5 billion almost completely without layoffs.

"It is irresponsible of DC 33 leadership to encourage its members to support a candidate who owes the city $380,000 in taxes right now," Simmons said. "The leadership urged its membership to vote for someone who is not tax compliant, someone who owes the city money at a time of financial crisis."

Street's debt to the city is listed at $388,037; he also owes the federal government more than $413,000 and the State of New Jersey $345,000, according to the New Jersey Division of Taxation website.

When learning of the Nutter campaign's comments, Street, the older brother of former Mayor John F. Street, said: "It sounds like a response from a frightened opponent."

Nutter received no union endorsements during the 2007 mayoral primary.

Democratic media strategist Neil Oxman, who worked on Nutter's first campaign, said the firefighters and District Council 33 endorsements reflected a general outrage with government at all levels.

"People are angry, they are scared, they are apprehensive. They are all these adjectives that have to do with living in a world uncertain economically," he said. "The people who are city employees are going to be the most angry because, in the long run, some of the world is going to have to change."

Contact staff writer Marcia Gelbart at 215-854-2338 or mgelbart@phillynews.com.