Front-runner Christine Quinn meets and greets Bedford-Stuyvest residents in Brooklyn as she announces her mayoral candidacy Sunday. Her initial rhetoric has been vague or noncommital, with platitudes like “I’m about keeping New York City a place for the middle class to live and grow.” So is everybody else.  We know plenty about Christine Quinn, who officially announced for mayor on Sunday, even though it feels as if she first started running for the job when Derek Jeter first ran out to shortstop for the Yankees.  We know how badly she wants to be the first female mayor of this city, how she would be our first openly gay mayor, how she worked her way up from being an activist and chief of staff to Tom Duane, another openly gay New York City politician, when he was on the City Council, before running to succeed Duane.  And we certainly know that Quinn decided to fold the City Charter into a paper airplane four years ago, overturning New York’s law about term limits so that Mayor Bloomberg could run for a third term. It wasn’t for the good of the city, just the good of Quinn, because she clearly thought she wasn’t ready to be mayor. Now she is, here we go.  But what we don’t know about Christine Quinn, and are about to find out, is whether she she can run for mayor and win by talking out of both sides of her mouth.  RELATED: CHRISTINE QUINN ANNOUNCES RUN FOR MAYOR  Quinn will run on her downtown, activist, Democratic roots. Or she’ll run on the last 12 years in New York as if she were Bloomberg’s No. 2.  But she can only pick one.  Quinn is a consummate politician, who has used brains and sharp elbows and a good, loud personality to turn herself into a consummate political insider. But at some point, as she tries to swing her way out of a crowded primary field and become the Democrat who takes City Hall back after 20 years of Rudy Giuliani and Bloomberg, she is going to have to tell the city what she actually stands for beyond ambition. And advocacy.  We get the part about how she would be the first female mayor, first gay mayor, all that. Now the job for her is to explain to the city what her message actually is.  RELATED: GIULIANI PENS FUNDRAISING LETTER FOR LHOTA  In making her announcement on Sunday, before a tour of the five boroughs, she said this: “I’m about keeping New York City a place for the middle class to live and grow.”  So is everybody else, from her Democratic opponents to Joe Lhota, the Republican who is probably the most interesting guy in the whole race. Quinn is going to have to do better than that. Unless she thinks she’s going to be running against people who are dead set against the middle class living and growing in New York City.  Quinn has the name, has big money behind her, clearly has the political chops to be the next mayor. What she does not yet have, despite all the people who want you to believe she’s been elected already, is a powerful rationale that voters can understand, and believe, about why she is ready to step up in class.  “First of all, no one cares who the front-runner is in March,” a prominent New York Democrat told me on Sunday. “If front-runners mattered, we’d be talking about Mayor Gifford Miller today.”
At some point, the City Council speaker, whose front-runner status may well prove fleeting, will have to decide whether to run as the progressive Democrat of her roots or the Bloomberg sidekick she has become. She cannot do both.