I live on Manhattan’s upper eastside, across from Gracie Mansion, the beautiful 1799 Federal-style house that overlooks the East River and is the residence of New York’s mayor and his family. On any given day I may see cops, TV cameras, and angry protesters in front of the Mansion, or buses discharging tourists, or dignitaries arriving in limos. And just as often I may see happy crowds, dressed in their finery and leaving the Mansion after a gala event. One evening some...