While Mayor Bloomberg’s political opponents hope the loss of the stadium will hurt his chances of re-election, yesterday’s vote against the plan could wind up helping the mayor in November, some campaign watchers said.

Until yesterday afternoon, when the Public Authorities Control Board in Albany rejected state financing for the proposed New York Sports and Convention Center, Mr. Bloomberg’s political rivals were united in their opposition to the facility. The domed stadium would have been the home stadium for the New York Jets and, Mr. Bloomberg hoped, the principal venue for the 2012 Olympics.

In the months leading up to yesterday’s vote, the Democrats united in their opposition to the stadium. Rep. Anthony Weiner prided himself on being the first of them to come out against the complex, which was planned for the far West Side of Manhattan, back in April 2004. The campaign of C. Virginia Fields, the Manhattan borough president, trotted out a three-and-a-half-year-old report about building housing and parks in the area instead of a stadium. The City Council speaker, Gifford Miller, and some of his colleagues sought to undo the mayor’s plan for the city to provide $300 million toward construction of a platform for the stadium. All four Democrats said city money would be better spent on schools, police, and other vital services.

The mayor, meanwhile, lobbied tirelessly for the stadium, which he and his deputy mayor for economic development, Daniel Doctoroff, made a centerpiece of a sweeping plan for redevelopment of a vast area of Manhattan at and near the Metropolitan Transportation Authority’s Hudson Rail Yards.

When the Assembly speaker, Sheldon Silver, and the Senate majority leader, Joseph Bruno, abstained yesterday in the vote of the control board, they crushed one of the mayor’s pet projects. They also, however, deprived the mayor’s opponents of what may have been their strongest campaign issue.

“In a curious way, this could wind up being good for Bloomberg as a candidate,” a professor of public affairs at Baruch College, David Birdsell, said. “In a way, this deprives his opponents of one of the best arguments against a Bloomberg mayoralty. It takes out of contention one of the most serious liabilities in terms of popularity, going into the general election.”

Although Mr. Bloomberg has argued for years that the stadium would be good for New Yorkers, many New Yorkers did not agree. According to the most recent poll by Quinnipiac University, released last month, New York City voters opposed the facility by 51% to 43%. According to a Marist Poll published this spring, New Yorkers rank education and jobs as their top priorities. The poll found that most New Yorkers interviewed expressed approval of the mayor’s overall record on economic development but disapproved of the stadium project.

After watching their boss spend so much time and political capital on the Sports and Convention Center, Mr. Bloomberg’s staff was reluctant to rejoice in the loss. There seemed to be a feeling among his advisers yesterday, however, that with the stadium off the table, Mr. Bloomberg would be free to focus on other, less controversial, topics.

“We have an increase in jobs. We’re building more ‘affordable housing.’ We are keeping crime down. The mayor has shown that the reforms he’s put into place in the school system are moving us in the right direction there,” a senior strategist for the mayor’s campaign, Bill Cunningham, said in a telephone interview. “That’s the record he’ll run on.”

He said anyone who would criticize the mayor on the basis of the stadium is probably just “jealous” of Mr. Bloomberg’s vision for shaping the city.

“They don’t have any vision of their own for this city. They don’t have a plan to create jobs, let alone a record for reducing crime, building affordable housing,” he said. “All of that is happening. They’re jealous of him, I would guess.”

He added that to “take delight” in the stadium news is an “embarrassment” for the mayor’s opponents, and an attitude that he said “underscores the fact that they have no program and no vision for this city.”

The politicians vying to unseat Mr. Bloomberg said they can’t see how the way the stadium proposal played out would help Mr. Bloomberg. Indeed, campaign officials said yesterday that Mr. Bloomberg’s steadfast focus on the stadium – and his ultimate failure to win approval for the project – are examples of his inability to provide the city with the leadership it needs.

“The stadium has consumed Bloomberg and his top deputy mayor’s time, and at the end there is noting to show for it – because it was a misplaced priority,” a spokeswoman for Fernando Ferrer, Jen Bluestein, said. “Three years of watching Mike Bloomberg chase like Captain Ahab after a stadium that would have had no positive effects on their daily lives is something most New Yorkers won’t soon forget during this campaign.”

A spokesman for Mr. Weiner, Anson Kaye, said the mayor’s “single-minded obsession” with building a stadium on the West Side rail yards had jeopardized the city’s chances of winning the chance to be host of the 2012 Summer Games.

“It is an issue that reflects the value system of this mayor and his preference to focus on a big-ticket development project in one corner of the city rather than a five-borough development campaign, and that’s certainly going to be an issue throughout the campaign,” the Weiner spokesman said.

A Miller spokesman, Reggie Johnson, and a Fields spokesman, Nick Charles, also indicated New Yorkers would use the stadium to judge the mayor. One of Mr. Bloomberg’s Republican opponents, Thomas Ognibene, said voters would look to the stadium as an example of how the “mayor was trying to dupe the people” into supporting something Mr. Ognibene said was essentially a political favor.

Some political consultants said the mayor’s opponents might be able to take advantage of the stadium’s apparent demise.

A veteran of New York City elections, Hank Sheinkopf, said if the Democrats can keep the memory of the stadium alive in voter’s memories and use it as proof that Mr. Bloomberg is out of touch, it could hurt the mayor’s chances. But he said there’s no assurance that the issue would not just die away, clearing the field for discussion of other issues like schools and crime.

“You don’t know what’s going to happen here yet,” he said. “You need to see how people react to it.”