The cheery poll numbers Mayor Bloomberg had been hoping for have finally arrived. He now holds a double-digit lead over the best-known Democratic candidate, Fernando Ferrer, and, if the election were held today he would soundly beat the other Democratic hopefuls as well in the race for City Hall.

“Obviously you have a bigger smile on your face when polls go up than when they go down,” Mr. Bloomberg told reporters on the Upper East Side yesterday after a Marist College Institute for Public Opinion poll showed he led Mr. Ferrer, a former Bronx borough president, 51% to 38%.”But there is only one poll that I worry about, and that is what takes place on November 8.”

The Manhattan borough president, C. Virginia Fields, also had reason to smile at the Marist numbers, which showed her running better than the other three Democrats in head-to-head matchups against the Republican incumbent.

The latest poll was anything but happy for Mr. Ferrer. In the Marist poll last month, he led Mr. Bloomberg 49% to 42%. That means the mayor picked up 20 percentage points against Mr. Ferrer in four weeks.

Analysts traced Mr. Ferrer’s reversal of fortune 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 murder six years ago, told the police group last month that the shooting was not a crime and that there was a push to “over indict” the officers involved. A jury cleared the officers of criminal charges, but analysts have said that Mr. Ferrer has been hurt by his recent comments because of the perception that he changed his position on the killing.

“It made Ferrer appear to be a very different person,” a political consultant, Hank Sheinkopf, said. “At this point, the body politic is clearly angry at Freddy Ferrer. He has managed to make Diallo overshadow the stadium discussion, and that’s why Bloomberg got the bump.”

Until now, Mr. Bloomberg’s campaign had been hobbled because of his support for a city- and state-subsidized stadium for the New York Jets on the West Side of Manhattan. Fully 52% of voters in the Marist poll said they were less likely to support Mr. Bloomberg because of the controversial project to construct a 75,000-seat stadium over the Hudson Rail Yards, with at least $600 million in taxpayers’ money. Mr. Bloomberg has said the project will help the city win the vote to be host city to the 2012 Olympics and will create thousands of new jobs.

Ms. Fields, like the other Democratic candidates, has opposed Mr. Bloomberg’s stadium plan, trailed the mayor in a head-to-head matchup by only six percentage points, 47% to 41%, the survey found.

“I thought we were going to grow through the primary,” Ms. Fields’s senior political adviser, Joe Mercurio, said. “Now I suspect we’re going to continue to grow, and it is going to be a two-way race with Freddy. I know this is pretty early, but the electorate is moving earlier. The partisan Democratic vote that doesn’t like Bloomberg is looking for a candidate and looking earlier.”

Mr. Ferrer, for his part, shrugged off the setback. “Polls are going to go up and down,” he told The New York Sun. “I’m not focused on them. I’m focused on the 1.1 million schoolchildren in this city and solving this education crisis so that every one of them has a quality education.”

Education is clearly at the forefront of voters’ minds. A 32% plurality of poll participants said education should be the top priority for the winner of the mayoral election in November. Another 21% said jobs needed to be the focus, and 19% said economic development was the most important issue facing the city. Against that backdrop, the mayor’s approval rating was up five percentage points, to 48% this month, Marist found. While 48% said it was time for a new mayor, 47% of those polled said Mr. Bloomberg should stay in City Hall.

The latest Marist College survey was conducted Monday and Tuesday among 525 people registered to vote in New York City, with the number of interviews in each borough based on the percentage of the citywide enrollment. The margin of sampling error is plus or minus 4.5 percentage points.

“What all this tells you is that the Diallo misstep impacted not just the minority communities but helped Bloomberg among the nonminority people too,” Mr. Sheinkopf said. “If you look at the Bloomberg numbers among minorities, his is in the 30s, which is very unusual for a Republican.”

Analysts also have been keeping a close eye on the battle between City Council Speaker Gifford Miller and Queens Rep. Anthony Weiner. They have been bringing up the rear in most of the polls.

In the new Marist results, in a head-to-head race against Mr. Weiner, Mr. Bloomberg takes 48% to the Democrat’s 36% – a nominally narrower gap than in the Bloomberg-Ferrer matchup.

Against Mr. Miller, Mr. Bloomberg fared a bit better, with a lead of 50% to 36%.

Analysts expect both men to pick up support as the months go on. Mr. Miller will have more time to campaign, they said, after the budget negotiations conclude next month. He also has been the most prolific fund-raiser among the Democratic candidates. And Mr. Weiner, whose district also includes parts of Brooklyn, appears to be picking up support in the outer boroughs.

“It is still early days,” Mr. Sheinkopf said. “This poll is like a biopsy so we can see how the patient is doing.”