I WAS almost scripted to hate Ed Koch from the moment in September 1977 when I moved, with a new Harvard doctorate, to Brooklyn, on what would become a long activist-writer’s foray into the city’s fiscal crisis and the effects of that summer’s power blackout and looting.

Mr. Koch was winning the Democratic mayoral primary, and my cousin James Wechsler, who’d been the editor of The New York Post in its liberal glory days but was then in charge of just the editorial page, was shaking his head in a lonely corner office on South Street as The Post’s new proprietor, Rupert Murdoch, turned it into a virtual press office for the Koch campaign.

Throughout his 12 years as mayor I assailed Mr. Koch — in a Brooklyn newspaper that I edited, in Dissent, in The Village Voice and even while working across the hall from him as a speechwriter for the City Council president, Carol Bellamy, whom the mayor at one point denominated, with his customary grace, “a horror show.”...