The easiest way to establish this is just to look at one of the formative moments of Giuliani’s political career. On Sept. 16, 1992, thousands of off-duty police officers crowded in front of New York’s City Hall to protest against Mayor David Dinkins. “The cops held up several of the most crude drawings of Dinkins, black, performing perverted sex acts,” Jimmy Breslin, the Newsday columnist, who was present at the riot, wrote. “ ‘Now you got a n****r right inside City Hall,’ one officer reportedly said,” Breslin continued. “ ‘How do you like that? A n****r mayor.’ ” Other officers chanted slogans like “Dinkins gotta go!” and “The mayor’s on crack!”

The cops were there to oppose a bill that would have removed the police from the city’s Civilian Complaint Review Board, an oversight body that handled allegations of police misconduct, and, crucially, would have made it independent of the police department itself. Faced with the prospect of potentially greater civilian accountability, New York City police officers took their anger to the streets.

Tensions were already high in the city — earlier in the summer, an officer had killed Jose Garcia, a young undocumented immigrant from the Dominican Republic, leading to protests and rioting — and fanning the flames on this particular day was none other than Rudy Giuliani, who had lost to Dinkins in the 1989 New York mayoral election.

Giuliani, the author Andrew Kirtzman recounts in “Giuliani: The Rise and Tragic Fall of America’s Mayor,” “walked to the flatbed truck outside the perimeter of the building, where thousands were gathered, and hopped up to the makeshift stage. After a handful of other politicians delivered their speeches, Giuliani took the mic and the crowd roared. Shedding his suit jacket and rolling up the sleeves of his white button shirt, he ripped into Dinkins.”

“The mayor doesn’t know why the morale of the New York City Police Department is so low,” he said, jabbing his finger in the air. “He blames it on me, he blames it on you. The reason the morale of the Police Department of the City of New York is so low is one reason and one reason alone: David Dinkins!”