New Yorkers can expect some targeted tax increases if one of three Democrats looking to succeed Mayor Bloomberg wins November’s election.

During a forum yesterday morning held by Crain’s New York Business in Midtown Manhattan, the three candidates defended their tax initiatives and panned Mr. Bloomberg for what they characterized as fiscal failures.

Within the last week, a Brooklyn-Queens congressman, Rep. Anthony Weiner; a former borough president of the Bronx, Fernando Ferrer, and the speaker of the City Council, Gifford Miller, have all announced initiatives that would raise taxes on certain groups.

The fourth candidate, the borough president of Manhattan, C. Virginia Fields, has not proposed any tax changes.

Mr. Weiner, whose congressional district includes parts of Brooklyn and Queens, is pushing a plan to implement an increase in the city income tax for those earning more than $1 million a year.

The change would increase their marginal tax rate to 4.67% from 4.45%.

The increase, Mr. Weiner said, will help pay for a 10% income-tax cut for New Yorkers earning $150,000 or less. With his plan, he has tried to position himself as the candidate fighting for the city’s middle class.

“I will pledge right here that, in a Weiner administration, I will not raise taxes on the middle class,” he told a group of business executives yesterday.

Mr. Miller is pushing a tax initiative that would extend the city’s personal income-tax surcharge, set to expire this year, for those making more than $500,000. He would use the new revenue, which he estimates will amount to $380 million a year, to reduce the number of students in overcrowded public-school classrooms.

He has also proposed levying taxes on insurance companies that are now exempt and using that money to provide a 5% across-the-board tax cut to businesses and a tax credit for small business owners whose profits, he said, are taxed twice.

Though several groups, including the Working Families Party, lauded Mr. Miller’s personal-income-tax proposal and another proposal he has floated to expand an earned-income-tax credit for low-income residents, the business community was not enthusiastic about his package.

The president and CEO of the Partnership for New York City, Kathryn Wylde, took issue with the plan for new insurance taxes.

“It’s really just shifting the burden to highly mobile, high-income individuals, and a major city employer: the insurance industry,” Ms. Wylde said during a phone interview late last week, just after Mr. Miller announced his proposal.

“It’s unlikely either the insurance industry or high-net-worth individuals would stick around for the privilege of giving everyone else a tax break,” she said.

Not to be outdone, Mr. Ferrer announced this week a proposal to reinstate a stock-transfer tax at the New York Stock Exchange. He would put the new revenue toward a court decision that requires more state financing for city public schools.

He would charge half a cent for every share purchased at $20 or more; 0.375 cents for stocks valued between $10 and $20,and 0.25 cents for stocks bought at a price of between $5 and $10 a share.

Mr. Weiner was the most aggressive critic of his opponent’s plan. Yesterday the congressman called it a “mind-bogglingly bad idea.”

All three of the tax plans would require state approval.

Rather than propose any tax changes now, Ms. Fields said yesterday that she would create a commission of “financial experts, business experts, and labor leaders” to address the city’s financial condition. She did not provide any additional specifics.

Meanwhile, when the candidates were asked at yesterday’s forum whether they would block construction of a stadium for the Jets if the city were awarded the 2012 Olympics, only Ms. Fields said she would not.

Mr. Bloomberg has argued that the stadium, which the administration calls the New York Sports and Convention Center, would act as an economic engine for the West Side. Messrs. Miller and Weiner indicated they would relocate the stadium to Queens, even if the project had been approved for Manhattan, as long as it was not too far along. Mr. Ferrer did not answer the question directly.

“I do not believe that stadium will be anywhere near half-built by the end of this calendar year, and neither does anyone else,” Mr. Ferrer said after the event. “That’s a hypothetical question; I’m giving you an actual answer.”

The Jets expect to start playing at the stadium in 2009.

The candidates also answered questions on issues ranging from the city’s deficit to attempts by Wal-Mart to open stores at sites in the five boroughs.

All of them criticized Wal-Mart, saying the retailer does not compensate its workers fairly and drives out small businesses. In February, community and political opposition led a developer to scrap its plans to build a Wal-Mart at Queens. Mr. Bloomberg supports bringing Wal-Mart to the city. He has said it will increase tax revenue.

In another campaign development, Ms. Fields, speaking in an interview shown last night on NY1, called on Mr. Ferrer to apologize for his statement that the killing by police officers of an unarmed immigrant, Amadou Diallo, was not a crime.