Christine Quinn leads her Democratic rivals in next year's race to succeed New York City Mayor Michael Bloomberg.

According to a NY1/Marist College poll released Monday, Quinn is 20 points ahead of her closest Democratic primary challenger, former City Comptroller Bill Thompson.

If elected next year, Quinn, who is preparing to marry her longtime partner, lawyer Kim Catullo, on May 19, would become the city's first openly gay mayor. And the first legally married, openly gay politicians to lead a major U.S. city.

In December, former Mayor Ed Koch endorsed Quinn's campaign after New York Police Department Commissioner Ray Kelly declined his calls to enter the race.

“I urged Ray Kelly to run for the last year-and-a-half. He told me he would not. I urged him again, he told me he would not. And when he decided he would not, I started backing Chris Quinn,” Koch said.

“I believe that she is the best one for New York because I think she'll be in the tradition of being in the center – a center candidate like I was center left,” he added. “I think she'll follow in the tradition of Mike Bloomberg, and of all the candidates, I think she has the most experience and the best philosophy to lead New York in these difficult times.”

The 45-year-old Quinn currently serves as Speaker of the New York City Council. Koch, Quinn and Bloomberg lobbied for New York's gay marriage law.