Reflecting a shifting dynamic in the mayoral primary race, the three candidates who were tied in second place in a recent poll spent the Democrats’ second mayoral debate yesterday clawing at one another with intensified vigor.

The latest Quinnipiac poll showed the Manhattan borough president, C. Virginia Fields, the speaker of the City Council, Gifford Miller, and a congressman who represents Brooklyn and Queens, Anthony Weiner, each with support from about one in five likely Democratic voters who picked a candidate, while the fourth contender, Fernando Ferrer, has the support of about two-fifths of the Democrats. He needs at least 40% in the September 13 primary to avoid a runoff with the second place finisher.

The candidates’ sense of urgency to distinguish themselves was apparent at yesterday’s debate, sponsored by WCBS-TV and moderated by two of the network’s political reporters, Andrew Kirtzman and Marcia Kramer, and the City Hall bureau chief of the New York Times, Jim Rutenberg.

The debate’s most lively exchanges belonged to Messrs. Miller and Weiner, who are considered by many analysts to be competing for the same base of support within the Democratic electorate.

Previously, Mr. Weiner had been largely ignored by his Democratic rivals, taking swipes at Mr. Ferrer with minimal response from the former Bronx borough president.

Yesterday morning, however, Mr. Miller seemed girded for battle with the congressman, launching quickly into an attack on Mr. Weiner’s various proposals for bringing financial relief to the city’s middle class. Mr. Weiner has built his campaign on the foundation of a proposed 10% income-tax cut for New Yorkers earning less than $150,000 a year, financed by a tax increase for city residents earning more than $1 million a year and the promised elimination or reform of the least efficient programs in the city budget.

Yesterday, Mr. Miller branded those proposals “gimmicks,” critiquing in particular Mr. Weiner’s recent outline for $1.7 billion in budget cuts, many of which are generalized promises of improved efficiency. Mr. Miller took special umbrage at Mr. Weiner’s promise to save the city $925 million by eliminating Medicare fraud without specifying how he would do it.

Mr. Weiner, in turn, excoriated Mr. Miller for his apparent disbelief that waste could be reduced in city government. “If you think we can’t cut out waste at least 5% like I proposed, you shouldn’t be mayor,” Mr. Weiner said.

The council speaker also came under fire for having promised to procure funds in the city budget to reopen firehouses closed by Mayor Bloomberg and then failing to follow through. Mr. Miller placed the blame on Mr. Bloomberg. When pressed by Mr. Kirtzman as to whether the failure to reopen the firehouses was a “broken campaign promise,” Mr. Miller replied that he was “making good” on promises made as council speaker by running for mayor.

Mr. Miller was also targeted for spending a large sum in taxpayer money on a series of mailings by the council that were widely perceived to be campaign literature. A spokesman for the council initially gave The New York Sun an estimate in June that the mailings cost taxpayers $37,000. In response to Freedom of Information Act inquiries, however, the council said the literature actually cost $1.6 million.

Mr. Miller disputed the notion that the huge discrepancy between his office’s initial estimate and subsequent accounting eroded his credibility or integrity. “Well, look, obviously, it was a mistake that was made,” he said of the initial estimate. “I think the fact that it was so obviously wrong shows that there was no intent to mislead.”

Ms. Fields expressed dissatisfaction with Mr. Miller’s reply, arguing that the money would have been better spent on many other city programs. “I know that $1.8 million would have gone a long way in terms of providing over 30,000 meals for seniors,” Ms. Fields said – at a cost of $60 per meal.

In the debate, Ms. Fields often found it difficult to get a word in. Seated next to Mr. Weiner at the end of the table, the borough president appeared to spend much of the debate clasping the talkative congressman’s hand in an effort to quiet him long enough for her to chime in.

Similarly absent from much of the back-and-forth was Mr. Ferrer, who appeared intent on avoiding any gaffes and spent most of the debate wearing an amused look while his rivals squabbled.

When he was not lying low, Mr. Ferrer’s debate strategy appeared to consist of painting New York as a metropolis in a state of ruin, using the words “crisis” and “crises” 13 times during the debate, mostly when describing the state of the city’s public schools and the availability of “affordable housing.”

Increasing the number of publicly subsidized housing projects and rent controlled residential units was the policy centerpiece of Mr. Ferrer’s performance yesterday, and when all four candidates were asked what the best thing Mr. Bloomberg had done for the city was, Mr. Ferrer replied that it was promising to build 65,000 units of “affordable housing.”

Mr. Miller and Ms. Fields answered that it was gaining control of the city’s schools, while Mr. Weiner replied: “I think the way he’s reduced racial tension in this city is commendable in a post-Giuliani era, and we should honor him for that.” In last week’s mayoral debate, Mr. Weiner was the only candidate to praise Mr. Giuliani as a superior mayor to Mr. Bloomberg.

While he succeeded in remaining quiet during the first portion of the debate, Mr. Ferrer was the subject of his rivals’ and the moderators’ prodding during the second portion of the exchange. Mr. Kirtzman faulted Mr. Ferrer for being missing in action over the last four years while not holding elected office, and Mr. Rutenberg and the other three candidates grilled Mr. Ferrer over an apparent flip-flop on the question of partial birth abortion, which he labeled a “barbaric practice” in 1997 but expressed support for in 2001. Mr. Ferrer said repeatedly that he thinks abortion should be “safe, legal, and rare.”

Perhaps the most intense criticism of Mr. Ferrer was reserved for his much derided plan to finance improvements to city schools by levying a $1 billion a year tax on Wall Street. The plan, which according to the Independent Budget Office stands to cost New York tens of thousands of jobs and which critics have said could drive Wall Street firms to New Jersey to escape the tax, has been dismissed even by many Ferrer supporters, including the speaker of the state Assembly, Sheldon Silver, whose approval would be required for Mr. Ferrer to implement the tax.

Yesterday, Mr. Weiner pointed out that another Ferrer backer, Eliot Spitzer, the attorney general and gubernatorial candidate, “reportedly said it was crazy.” Mr. Ferrer then shot back, “You can’t make things up, Anthony. Come on.” Later in the day, the Weiner campaign pointed to an article in the New York Post in which Mr. Spitzer was reported to have told Mr. Ferrer that the stock-transfer tax was “a dumb idea” and “unworkable.” A spokeswoman for Mr. Ferrer, Christy Setzer, clarified yesterday that it was the term “crazy,” and “the over-the-top language that we’ve not seen or heard, that’s what Freddy was objecting to.” A spokesman for Mr. Weiner, Anson Kaye, responded: “If the Ferrer campaign is conceding that what Eliot Spitzer said is that it’s dumb and unworkable, we agree with that.”