Mayor Bloomberg’s popularity is mounting and his lead over his political rivals is expanding, according to poll results released yesterday.

Two years ago, only 31% of New Yorkers said they approved of the job Mr. Bloomberg was doing at City Hall. According to the Quinnipiac poll released yesterday, a full 60% of New Yorkers now approve of the sitting mayor’s work. That’s up five percentage points from June, the last time the polling institute asked the question.

The distance between Mr. Bloomberg and the Democratic frontrunner in the mayoral race, Fernando Ferrer, widened to 16 points from 13 points in June. In March, Mr. Ferrer was ahead of the mayor, with 47% of respondents saying they would vote for him and 39% saying they would reelect Mr. Bloomberg.

According to the polling data released yesterday, Mr. Ferrer has slightly more Democratic support than Mr. Bloomberg, winning 47% of the vote, compared to 42% for the mayor, but Mr. Bloomberg would win 76% of the Republican vote, compared to 16% for Mr. Ferrer. And although Mr. Ferrer has far more Hispanic support than the incumbent, Mr. Bloomberg, an Upper East Side billionaire, is more popular among black voters than Mr. Ferrer, with 45% of the vote versus Mr. Ferrer’s 43%.

“Looking at Mayor Bloomberg’s numbers, the Democrats might have to take some comfort from that great philosopher Yogi Berra: It ain’t over till it’s over,” the director of the Quinnipiac University Polling Institute, Maurice Carroll, said. “But at this rate, New York City Republicans could stay home on Election Day. The mayor could win this one with Democrats and independent voters.”

The rankings of the Democratic candidates remained unchanged in the poll, but the City Council speaker, Gifford Miller, who has been tying for last place for the past few months in the polls, surged forward. If the primary had been held last week, Mr. Miller would have won 15% of the vote, just one point less than the Manhattan borough president, C. Virginia Fields. Mr. Ferrer is still the clear front-runner, with 33% of the vote, but if Mr. Miller’s surge continues, he could surpass Ms. Fields and wind up in a runoff election with Mr. Ferrer.

At this point, though, most New Yorkers say the Democrats blend together on the issues. According to the Quinnipiac poll, 55% of voters said there was either no difference or a minor difference between the Democrats on the issues.

Mr. Carroll said it appears that Mr. Miller “is making a move. Fields and Weiner are fading in the stretch.”

The poll was conducted between July 12 and July 17. On July 15, The New York Sun and other publications reported that mass mailings by the City Council featuring prominent campaign-style photos of Mr. Miller cost $1.6 million, while the speaker’s office had earlier estimated the cost at $37,000.

A veteran political consultant, Hank Sheinkopf, said it’s unclear how the mailings scandal could affect Mr. Miller’s chances, but he said the campaign is far from over.

“Miller’s on the move,” Mr. Sheinkopf said, adding that he could continue to gain on Ms. Fields and Mr. Ferrer as the campaign moves forward.

“We haven’t seen any television from Gifford yet,” he said. “We haven’t seen any mass communications from people yet. It is still too early to call the primary.”

The poll, which surveyed 1,313 New York City registered voters and has a margin of error of 2.7 percentage points, also found that most voters are happy with “the way things are going in New York City today.” A full 66% of voters said they were somewhat satisfied or very satisfied with the city’s direction.