He's not any of the usual New York categories: social liberal/fiscal conservative, for example, or white-ethnic conservative, or Manhattan Liberal. He's got some of the New York City Partnership's brand of Rockefeller liberalism (that's the part of him that's comfortable with raising taxes, and which festoons Central Park with saffron banners). But he's no activist, and has generally avoided using government to advance a real liberal agenda, fighting a bill that would have used city contracts to advance gay rights, and keeping his mouth shut about the war.

Nobody's cast it this way yet, but his recent foray into a piece of housing policy called "inclusionary zoning" is, in a way, the most liberal thing he's ever done. Observers are certainly surprised. City Limits, the liberal monthly, leads its useful introduction to the the debate by noting, "It's already gone further than anyone thought it would."

The basic idea of the policy -- proposed for Williamsburg and the far West Side of Manhattan -- is that developers will be permitted to add a couple of floors to planned buildings if they include some apartments for low- and middle-income people. Democrats led by Councilman David Yassky have been pushing this, and it's currently in vogue in liberal planning circles.

The advantage is that it allows city's to produce affordable housing without spending taxpayers' money or putting onerous requirements on developers.

The risk is that developers who aren't permitted to go to the full, "inclusionary" height without adding affordable apartments might not build at all.