By Edith Honan
NEW YORK (Reuters) - New York mayoral candidate Bill de Blasio has a strong lead ahead of Tuesday's Democratic primary, though his support is just shy of the threshold needed to avoid a runoff, according to two polls released on Monday.
De Blasio, the city's public advocate, has the support of 39 percent of likely Democratic voters, according to a Quinnipiac poll, with an NBC 4 New York/Wall Street Journal/Marist poll finding him the pick of 36 percent of likely voters.
According to the city's election rules, if no Democrat wins more than 40 percent of the vote, the top two candidates will compete in a runoff election, due to be held October 1.
De Blasio's main opponents, City Council Speaker Christine Quinn and former City Comptroller Bill Thompson, trail by double-digits, locked in a tight race for second place.
The Quinnipiac poll has Thompson leading Quinn 25 percent to 18 percent, while the Marist poll has the pair tied at 20 percent.
"Will de Blasio avoid a runoff or will we have a battle of the Bills? Flip a coin," said Maurice Carroll, director of polling at Quinnipiac, who noted that 8 percent of likely Democratic voters remained undecided.
The city's outgoing mayor, Michael Bloomberg, has broken his silence on the race, calling Quinn the best choice on the Democratic side and suggesting that de Blasio, who has waged a populist campaign around the idea of income inequality, is seeking to divide New Yorkers.
In a wide-ranging interview with New York magazine, published over the weekend, Bloomberg said he thought de Blasio was engaging in class warfare and relying on his biracial family to build support among minority voters opposed to aggressive "stop-and-frisk" police tactics.
De Blasio, who is white, is married to a black woman, and the couple's son, Dante, appeared in a campaign ad touting de Blasio's opposition to stop and frisk, which overwhelmingly singles out young black and Latino men.
The Democratic nominee will face the Republican candidate on November 5. Front-runners in the Republican contest are Joe Lhota, former head of the city's mass-transit agency, and businessman John Catsimatidis.
De Blasio's emergence as front-runner among Democrats in August was the latest twist in the turbulent race to succeed Bloomberg. For months, Quinn, a Bloomberg ally who would be the first female and openly gay New York mayor, maintained a strong lead.
Her dominance was first challenged this spring when Anthony Weiner - once a popular liberal congressman who resigned two years ago in a lewd picture scandal - entered the race, saying he hoped voters would give him a second chance.
Weiner surged ahead of Quinn in the polls, only to see his candidacy disintegrate after new revelations about relationships he had with women he met online.
The Quinnipiac poll now has Weiner at 6 percent, while the Marist poll has him at 7 percent.
In the race for New York City comptroller, Manhattan Borough President Scott Stringer pulled further ahead of former Governor Eliot Spitzer among Democratic likely voters, 50 percent to 43 percent, according to the Quinnipiac poll.
Polls have been inconsistent on Spitzer's attempt to make a political comeback after a prostitution scandal forced him to resign the governorship in 2008. Marist reported on Monday that Spitzer was slightly ahead by 2 percentage points, 47 percent to Stringer's 45 percent.
Quinnipiac's survey of 782 likely Democratic voters was conducted from September 6 to 8 and had a margin of error of plus or minus 3.5 percentage points. The Marist survey of 936 registered Democrats was conducted September 3 to 6 and had a margin of error of plus or minus 3.2 percentage points.
(Reporting by Edith Honan, additional reporting by Hilary Russ; Editing by Scott Malone, Eric Beech and David Gregorio)