By NICHOLAS CONFESSORE

It was little surprise yesterday when Anthony D. Weiner, the congressman from Brooklyn, declared himself a candidate for mayor. After all, formal announcement or not, Mr. Weiner has been actively campaigning around the city, lobbing criticism at his Democratic rivals and slogans at voters, for the better part of a year.

But the announcement - actually, five announcements, one in each borough-marked the start of what will probably be a much more active period of campaigning for Mr. Weiner, who has been struggling to hold down his day job in Washington while campaigning in New York with the same regularity as the other three Democratic candidates for mayor.

"What I'm going to do is recognize, value and honor the hard work of the people of this city," he said yesterday at City Hall, flanked by union workers and other supporters. "All too often, we open up the newspapers and turn on televisions, and it seems like New York is all about someone else."

The same might be said of the mayoral race, which in recent weeks has shown Fernando Ferrer well ahead of Mr. Weiner and the other Democratic candidates, and Mr. Bloomberg handily defeating any of them in a head-to-head match. Mr. Weiner, however, said yesterday that the recent end of the congressional session and a busier August campaign schedule would raise his profile among Democratic voters just as they begin to pay close attention to the race.

"Fortunately, I've had the high honor of representing the people of Brooklyn and Queens every day, fighting the Bush agenda," he said. "Now I'm back and I'm campaigning full time. We're going to have millions of dollars in TV commercials started, but I want to make it very clear in all five boroughs how seriously I take this race."

He cited a recent Marist Poll showing that he; the City Council speaker, Gifford Miller; and the Manhattan borough president, C. Virginia Fields, were closer than they had been in weeks.

Mr. Weiner's most immediate obstacle in the primary is Mr. Miller, who has recently gained some traction in the race. With Mr. Ferrer receiving wide support among Hispanic voters and Ms. Fields expected to do well among blacks, both Mr. Weiner and Mr. Miller are hoping that a strong showing among white middle-class voters - especially in the boroughs outside Manhattan - will put them into the expected runoff election.

Mr. Weiner has taken pains to depict himself as the candidate of ideas, all of them meant to appeal to white, middle-class voters: he proposes cutting taxes, cleaning up government waste, and supporting the causes of labor unions. He even said yesterday that people should not support him because he grew up in Brooklyn or because he has experience in Congress, but "based on the ideas."

But Mr. Weiner, who represents parts of Brooklyn and Queens and grew up in Park Slope, has built his campaign more on biography than Mr. Miller, who was born on the Upper East Side. He embeds his proposals in a broader message featuring his Brooklyn roots and middle-class upbringing.

"Living in the neighborhoods of Brooklyn I learned a great deal about what it means and how difficult it is for the working class in this city, and those struggling to make it," he said yesterday.

With about $1.7 million in cash on hand, Mr. Weiner expects to unveil television ads in mid- to late August that stress those very themes.

Yesterday, Mr. Miller picked up an endorsement in Mr. Weiner's proverbial backyard, from Representative Gary Ackerman, a Queens Democrat. Mr. Ackerman cited Mr. Miller's leadership in the Council, saying that he had "proven himself to be a master at bringing people together, reasoning with them, coming up with ideas and platforms and proposals that can sell."

Mr. Ackerman was careful not to criticize Mr. Weiner or the other candidates, saying that he had made a "choice among friends" and had "nothing bad to say about any of the other candidates that are running."

Adding to a string of endorsements by labor unions, Mayor Michael R. Bloomberg was endorsed yesterday by Service Employees International Union Local 32BJ, which represents 60,000 doormen, janitors, security guards and other building service workers in the city.

"Local 32BJ members and working families need a mayor who can deliver good jobs, living wages and a safer city for all New Yorkers," said Mike Fishman, president of the local, at a news conference in Manhattan attended by the mayor. The union praised zoning changes enacted under Mr. Bloomberg that have led to housing construction in West Chelsea and Williamsburg and Greenpoint in Brooklyn.

Mr. Fishman also said his union's members had benefited from legislation, signed by the mayor in 2002, strengthening job protections when buildings are sold or labor contracts are transferred, and a program established in May that trains private security guards to identify explosives and false identification.