On the corner of Canal and Varick Streets at the moment sits a 15,000-square-foot plastic tent, one that required a week’s worth of construction, the kind of edifice that typically at this time of year is given over to the sale of hand-knit scarves and tiny things made of wood. The purpose of this particular tent is outside the scope of holiday crafts: The project, called Talking Transition, was developed by a consortium of nonprofit groups, including the Revson Foundation, to allow New Yorkers to voice their opinions about what sort of direction the city should take in the aftermath of Bill de Blasio’s victory in the mayor’s race.

Filled with stacked milk crates, the tent, through which more than 5,000 people have already passed, is meant to convey a soapbox theme. Rows of tablet computers allow visitors to answer survey questions, the data eventually to be compiled and disseminated.

The mission is nonideological, a spokeswoman for the venture informed me, but the tone is decidedly leftist. Panel discussions are devoted to subjects including the plight of low-wage workers and the difficulties the poor and the vulnerable face gaining access to health care. Walls are lined with handwritten notes giving expression to what New Yorkers would like to see more of, none of it surprising: higher-paying jobs, affordable housing, equality. One note simply reads, “Love.”

The certainty with which it seemed a year ago that Christine C. Quinn would be the next mayor has left some to interpret Mr. de Blasio’s ascension as itself a kind of pop-up enterprise. His longtime supporters like to joke about how difficult it was to get reporters to come listen to him in April. But the modern progressive politics on which he has risen to power, the politics that in New York now exist at the fashionable center rather than on the outcast periphery, have deep and expansive roots in the city, roots that predate the Occupy movement and originate largely in the creation of the Working Families Party.