Quinn made the formal announcement during a walking tour of the Big Apple that The New York Times described as an intimate "contrast to the businesslike style of Mayor Michael R. Bloomberg."
The Times said Quinn and Bloomberg, who is not seeking re-election, have actually been political allies at City Hall, which the newspaper said could present a challenge of reaching voters outside Manhattan.
To soften her image as a hard-nosed city politician, Quinn released a biographical video stressing her middle-class upbringing and concern for voter-friendly issues such as good schools and child care.
The video did not touch on Quinn's sexual orientation and relationship with longtime partner Kim Catullo, whom she married last year, the Times said.