Poll: New frontrunner in NYC Democratic mayoral race

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(CNN) - In a surprising switch-up, a new poll indicates Public Advocate Bill de Blasio jumped to the front of the Democratic primary race for New York City mayor.

According to the Quinnipiac University poll released Tuesday, de Blasio has the support of 30% of likely primary voters, with City Council Speaker Christine Quinn–the former frontrunner–falling behind with 24% and former Comptroller Bill Thompson taking in 22% just four weeks before the September 10 primary.

Former Rep. Anthony Weiner remains behind all three at 10%, while Comptroller John Liu has 6% support.

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"A few weeks ago, Public Advocate Bill de Blasio looked like an also-ran. Today, he's the leader of the pack, and a winner in the runoffs," said Maurice Carroll, director of the Quinnipiac University Polling Institute. "Follow the bouncing ball, folks. This line-up keeps changing."

The new survey adds an interesting twist just hours before the Democratic candidates square off in a televised debate Tuesday night.

De Blasio released his first television ad last week as the poll was being conducted. Sworn in as public advocate in 2010, the city's second highest elected office, de Blasio's past work includes managing Hillary Clinton's first U.S. Senate bid from New York in 2000 and serving in the City Council for eight years, representing Brooklyn neighborhoods.

A Quinnipiac survey last month showed de Blasio gaining ground in the primary, as Weiner's numbers fell amid his renewed sexting scandal. Quinn remained at the top with 27% of support among likely Democratic voters, with de Blasio not far behind at 21% and former comptroller William Thompson at 20%. Weiner, meanwhile, was at 16%.

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If a candidate fails to capture 40% of the primary vote next month, the race automatically goes into a runoff between the top two contenders.

Should that be the case, the new poll indicates de Blasio would topple Quinn 54%-38% in a runoff, with a narrower margin over Thompson, 50%-41%. In a hypothetical runoff against Weiner, de Blasio would best the former congressman 72%-22%.

"Nobody thinks former U.S. Rep. Anthony Weiner will pack it in, but 55 percent of all voters wish he'd go away and 51 percent of Democrats say they'd never vote for him," Carroll added in a news release about the poll.

If Thompson and Quinn make it into a runoff, the survey shows the former comptroller would beat Quinn 51%-41%.

But Tuesday's numbers hardly indicate a solid prediction of what will happen on September 10; only 46% of likely primary voters say they'll definitely vote for the same candidate they support today. Thirty-four percent say they are likely to change their mind, with only 16% saying they are likely to choose someone else.

For the survey, Quinnipiac interviewed 579 likely Democratic primary voters by telephone from August 7-12. The sampling error is plus or minus 4.1 percentage points.