A poll released yesterday found that more than half the voters think it’s time for a changing of the guard at City Hall.

A Marist College Institute for Public Opinion Poll found that 53% of registered voters who participated said it was “time to elect someone else” for mayor, while 42% said Mayor Bloomberg deserved a second term. The rest said they were unsure.

The poll also showed that if the election were held today, a former Bronx borough president, Fernando Ferrer, would best the mayor 51% to 39%. In September, when Marist last asked voters about whom they supported, Mr. Ferrer beat Mr. Bloomberg by 47% to 43%, but that was well within the poll’s margin of error.

Mr. Bloomberg is essentially tied with the other likely Democratic contenders. He and the Manhattan borough president, C. Virginia Fields, and the City Council speaker, Gifford Miller, would be in a dead heat were the election held now, the poll found. Mr. Bloomberg would only narrowly defeat a Brooklyn-Queens congressman, Anthony Weiner, and a council member from Brooklyn, Charles Barron.

The poll was not uniformly gloomy for the mayor.

For one thing, it found that only 39 percent of respondents said they were “strongly committed” to their choice of a Democratic candidate.

Moreover, the mayor’s approval ratings, which have been on the upswing, continued to climb. The poll found that he has a 46% approval rating, up 4 percentage points from September. He is most popular in Manhattan, the Bronx, and Staten Island, where his approval rating breaks through the 50% mark.

Similarly, his approval rating among white voters was 52%, the poll found, though it was just 37% among Latino voters and 36% among black voters. The mayor also got good marks from those polled by Marist for the way he handled security, crime, and race.

He is still struggling to convince New Yorkers about his school reform and the budget, however, and he also received low marks on taxes and his contract negotiations with city employees, the poll said. The city is at an impasse with the police, firefighters, and teachers unions. The police are in binding arbitration now. The teachers are about to go to a process called fact-finding, which is meant to push the two sides toward some amicable contract settlement.

Nevertheless, 52% of those polled said they thought the city was “headed in the right direction,” up from 48% in September.

The survey, conducted Dec. 8 and Dec. 9, had two parts: A total of 701 residents were questioned, with a margin of error of plus or minus 4 percentage points. For questions posed to the 503 registered voters in the sample, the margin of error is plus or minus 4.5 percentage points.