Elmo was strolling around. So was Cookie Monster, each posing for pics. It was another day in tourist-packed Times Square with its mind-numbing array of family-friendly draws. Bill de Blasio was here for a different reason—to pick up the endorsement of the musicians union, which chose the 52-year-old mayoral candidate for (among many reasons) his ambitious plan for affordable housing. The city's musicians, so crucial to tourism, are getting pushed out of the city, says K.C. Boyle, political director of Local 802 of the Associated Musicians of Greater New York.

A generation ago, any political event in Times Square would have been competing with hookers, not Muppets. Crime famously drove New York politics. It helped elect Ed Koch in the '70s and '80s, Rudy Giuliani in the '90s, and Mike Bloomberg for three terms that are ending now. (New Yorkers may well have elected a Democrat 12 years ago but primary day was 9/11, the election was postponed, and Bloomberg and his checkbook won.) But with crime down and Freedom Tower up, personal safety is just not the same issue.

How sure is the progress? Can New York slip into Detroit-like fiscal chaos, as Bloomberg recently said? "It can't happen," de Blasio told National Journal at a coffee shop near Gramercy Park, noting how much stronger New York is financially. And, he argues, the city's progress on crime is irreversible. He says this a day after a federal judge issued a rebuke to Bloomberg's stop-and-frisk policies and the mayor strongly hinted that lives would be lost. De Blasio notes that the crime fight, like winning the Cold War, took place under many leaders—he does a hat tip to neighborhood groups, too, and declares the war won. "It's been two full decades of progress," de Blasio says, picking at a pastry. "It's fear mongering to suggest" the reduction in crime could be reversed.

A former city-council member, who now holds the relatively new post of public advocate, de Blasio is claiming the boldest break with the Bloomberg era on everything from crime policy to economic development. (He likes Bloomberg on trans fats, not so much on congestion pricing for cars in Manhattan.) His proto-populism has tickled the erogenous zones of the city's liberal elite. de Blasio has been endorsed by The Nation and District 1199 of the Service Employees International Union, the city's biggest union. New York may have elected Republicans like Giuliani and Bloomberg (before he became an independent) and even John Lindsey. But at its heart, it's a liberal city—President Obama got 81 percent of the vote here—and without crime or aberrations like 9/11, it's a new day.

In a chaotic, crowded field, polls can be decidedly unreliable. Still, de Blasio leads among Democratic candidates in a new Quinnipiac poll, one with a 4.1 percentage-point margin of error. He's one of a few first-tier candidates when the polls open on Sept. 10. If no candidate clears 40 percent—and that seems almost certain—there will be a runoff.

The leading candidate in terms of wealth and experience, and notoriety, has been City Council Speaker Christine Quinn, who would be the city's first female mayor. With a strong record of accomplishment (from budget to expanding kindergarten), a compelling story (gay, fair housing advocate), and the visibility that comes from being the Council president, she's been the frontrunner from the start. Bill Thompson, the city's comptroller, has the powerful teachers union behind him and would be the first African-American mayor elected since 1989.

There are others, including, ahem, Anthony Weiner, who continues to get a good response from crowds. At the free Toni Braxton concert in Crown Heights this week, he got a lot of shout-outs from the African-American crowd.

In a sign that his top competitors see the gains he's posting, de Blasio took a lot of fire at Tuesday night's mayoral debate, with Weiner at one point saying de Blasio couldn't stand Quinn becoming speaker. For his part, de Blasio linked Quinn and Bloomberg at every opportunity.

How did de Blasio get here? By being a dedicated pol. Kid comes to NYU in the '80s. Gets involved in politics—neighborhood groups, school boards, works on tons of campaigns. He manages Hillary Rodham Clinton's 2000 Senate bid. He works with Andrew Cuomo at the Housing and Urban Development Department. He's close to Harold Ickes, the famed Clinton consigliere. (Oops. He was a big John Edwards ally, even traveling to Iowa to help.) But like most people, his family life is more interesting. He was born with the last name Wilhelm and changed it as he grew closer to his mother. His wife, the African-American poet Chirlane McCray, had been a self-identified lesbian before they met. Their son, Dante, who sports a large Afro, has become a rock star on the campaign, and was the centerpiece of the first TV ad.

In a city where racial politics are as complicated as ever, it's hard to know if de Blasio's "modern family," as The New York Times put it, will help him make enough inroads among, say, black voters or anyone else to make the runoff. But de Blasio is making a play, shaking hands in Harlem, or bringing Dante to that same Toni Braxton concert. Others argue that the black vote will gravitate toward Thompson, putting de Blasio out of the running. See Tuesday's smart piece from The Guardian.

For his part, de Blasio insists that his surtax on the rich—those making over $500,000—and other policies would be more beneficial to the city in the long run. It's not addressing inequality that'll make the city poorer, he argues, saying pricing musicians out of the city does not help the tourist industry. "He's trying for an inside straight, saying 'I'm the most anti-Bloomberg candidate,'" says Mark Green, who de Blasio ousted from the public advocate post, adding that that might be enough in a multi-candidate field.

Can de Blasio's vision sell? Howard Wolfson worked closely with de Blasio on the Hillary Clinton Senate race in 2000. They were on 7:30 a.m. conference calls for more than a year. Now Wolfson is deputy mayor under Bloomberg and, not surprisingly, doesn't embrace the critique of the current mayor. "Bill is a friend," Wolfson told me. "But he has set forth a vision for the city that is very explicit--higher taxes, bigger government, more regulation, more mandates on business, and in my opinion we tried that model and it failed." After an "I respect Howard" qualifier, de Blasio dismissed that as "misleading" and "fear mongering."

A Quinn ally depicts de Blasio as pugnacious and indiscriminate: "You have to know when to fight and when to work together. The council president understands that." And that's a good point. Besides, Quinn isn't the Bloomberg quisling that de Blasio lampoons. Still, her nuanced positions—she'd be inclined to keep the current police commissioner, Ray Kelly, but instruct him to overhaul the stop-and-frisk policy he championed—are, as de Blasio suggests, a bit flaccid.

Whatever happens here will be watched closely, especially by would-be mayoral candidates. In city halls across the country, mayors face a familiar and unforgiving chore of balancing the needs of developers and neighborhoods while presiding over chaotic public schools, keeping up decaying infrastructure, and pleasing the ratings agencies (whose word still counts, despite the financial crisis). If Bill de Blasio can make it here, other populists are sure to try and, to paraphrase Frank Sinatra, make it anywhere.