When it came to scandal, the Tammany leader Big Tim Sullivan said, New York was a nine-day town. But in the case of the murder of his friend Herman “Beansie” Rosenthal, a gangster and gambling house proprietor, Sullivan’s adage proved spectacularly untrue. Charles Becker, an NYPD lieutenant, was one of five men convicted of the murder, all of whom were sent to the electric chair. Though the case was sensational and the conviction a travesty, Becker is little remembered today, and defended less. Both failures are all the more disgraceful because the prosecution was undertaken for a noble cause, that of political reform in general and police reform in particular.

As with any criminal trial that is transformed into social allegory, the cause trumped the case; facts that contradicted it were held not as false but as heretical, demanding suppression instead of debate. Later generations seeking lessons from the past are likelier to dwell on episodes of clear-cut triumph or transgression. Who wants to commemorate a battle without heroes?

In most tellings of the city’s political history, the struggle between Tammany Hall and Reform is recounted in nearly Manichean terms. The gangsterism and graft of Tammany sometimes reached a stupendous scale, but the machine also represented the largest part of New York City, with all its immigrant energy, and its legacy includes the New Deal. For what it was worth, its lack of affectation was commensurate with its lack of principle, as when Alexander “Clubber” Williams, a police inspector, replied when asked why he failed to close the brothels in his district: “Because they were kind of fashionable at the time.” In Tammany’s case, a sense of humor was a not-quite-saving grace, but it pointed to the pragmatism that accounted for its durability and many decencies. By contrast, Jacob Riis lamented that every reform movement—a term broad enough to encompass opponents of 80-hour workweeks and naughty postcards—ought to be assigned an official humorist, to save them from conceit and worse.