Mayor Bloomberg landed another set of cheery poll numbers yesterday. The latest Quinnipiac University poll showed him pulling ahead of the longtime Democratic front-runner, Fernando Ferrer.

The poll, released yesterday, found Mr. Bloomberg ahead of the former Bronx borough president by 47% to 38%, representing a stunning 15-point drop for Mr. Ferrer in the poll since March.

“The mayor has a nine-point lead, which is better than being six points down,” the poll’s director, Maurice Carroll, said. “And this is before Bloomberg taps into his multi-million-dollar war chest for TV commercials and mailings.”

In the poll, Mr. Bloomberg held a narrower lead, 43% to 38%, over the Manhattan borough president, C. Virginia Fields. She now appears to be the Democrat in the best position to challenge the mayor.

“The spread between Virginia and Bloomberg is pretty close to the margin of error, so you certainly can’t say that Mayor Bloomberg has put this away by any stretch of the imagination,” the president of the political consultancy Advance Group, Scott Levenson, said yesterday.

The Quinnipiac poll only adds weight to the poll released two weeks ago by the Marist College Institute for Public Opinion that showed Mr. Bloomberg leading Mr. Ferrer by 51% to 38%. In that poll, Ms. Fields was running better than the other three Democrats in head-to-head match-ups against the Republican incumbent.

Quinnipiac’s polling had a similar finding.

“Both polls are tapping into something,” a Baruch College political-science professor, Douglas Muzzio, said. “This is crystallizing into a two-tier race. It used to be Freddy and the rest, and now it is Freddy and Virginia and the rest.”

Among Democratic primary voters, the horserace is still between Mr. Ferrer, at 27%, and Ms. Fields, at 23%. That’s down from a 40-to-14% Ferrer lead at the beginning of March. Rep. Anthony Weiner of Queens and the City Council speaker, Gifford Miller of Manhattan, are still in low double digits. In the Quinnipiac poll, Mr. Weiner got 13% of the Democratic support and Mr. Miller 11%. About one-fourth of Democrats in the poll did not back a candidate.

“Freddy has gone from 40 to 27 and we’ve gone from 13 and 14 to 23 and 30,” a political consultant who is advising the Fields campaign, Joseph Mercurio, said. “Back when they invented the whole concept of runoffs, they said it was going to prevent a minority candidate from winning. Here we are and you are probably going to have two candidates in the runoff, one Hispanic and one black.”

If the top vote-getter in the mayoral primary does not receive 40%, then a runoff election is held between the top two finishers. In 2001, Mr. Ferrer finished first in the primary but lost to the city’s public advocate, Mark Green, in the runoff. Mr. Bloomberg defeated Mr. Green by 35,000 votes in the November election.

Breaking the Quinnipiac numbers down further, Mr. Ferrer had the support of 62% of Hispanic Democrats, 23% of blacks, and 17% of whites. Ms. Fields had 40% of black Democrats, 12% of Hispanics, and 16% of whites.

Mr. Ferrer’s reversal of fortune, and his thin support among blacks, can be traced to comments he made in mid-March to an audience of police sergeants about the killing of an unarmed West African immigrant, Amadou Diallo, by police in 1999.

Mr. Ferrer, who was arrested while protesting the Diallo slaying six years ago, told the police group in March that the shooting was not a crime and that there had been a push to “over-indict” the officers involved. A jury cleared the officers of criminal charges, but analysts have said Mr. Ferrer has been hurt by his recent comments because of the perception that he changed his position on the killing.

Of the 57% of New York City voters who said they had heard or read about Mr. Ferrer’s comments on the Diallo case, 47% said his comments made them think less favorably of him, yesterday’s poll found. Among black voters who have heard of the remarks, 62% said they thought less favorably of Mr. Ferrer as a result, the survey found.

While Mr. Bloomberg stacks up better than before against the competition, his overall approval rating has not changed much. He has a 47%-to-41% approval rating and voters are split 47% to 47% on whether he cares about their needs and problems. On the brighter side for the mayor, 74% of those surveyed think he has strong leadership qualities.

From May 3-9, Quinnipiac University surveyed 1,169 New York City registered voters. The margin of error for the poll is plus or minus 2.9 percentage points. On the question of the Democratic primary, asked only of the poll’s 707 registered Democrats, the margin of error was plus or minus 3.7 percentage points. For subgroups such as Hispanic Democrats, it is wider still.