In 1984 the governor of New York was Mario Cuomo, father of the current governor. The elder Cuomo, who died on New Year’s Day 2015, will be best remembered for his keynote address at the 1984 Democratic National Convention, in San Francisco. It is the most famous political speech of our time not given by Ronald Reagan. It was an eloquent defense of traditional American liberalism as preached and practiced by presidents from F.D.R. to Adlai Stevenson. (What? You say Adlai was never president? That's not how my mother remembers it.)

Cuomo's theme was “a tale of two cities,” although the metaphor got away from him and sometimes it was just one city with two parts. Cuomo laid it on thick. Reagan, he said, could see one part of the city from “the veranda of his ranch.” That part looked fine and healthy. But there was another part to the shining city:

the part where some people can’t pay their mortgages . . . , and middle-class parents watch the dreams they hold for their children evaporate. In this part of the city there are more poor than ever. . . . There are elderly people who tremble in the basements of the houses there. And there are people who sleep in the city streets, in the gutter, where the glitter doesn't show. There are ghettos where thousands of young people . . . give their lives away to drug dealers every day. There is despair, Mr. President, in the faces that you don't see, in the places that you don't visit in your shining city.

Besides Dickens, this was a hat tip to Benjamin Disraeli, the 19th-century British prime minister and novelist, who famously wrote about “two nations; between whom there is no intercourse and no sympathy; who are as ignorant of each other’s habits, thoughts, and feelings, as if they were dwellers in different zones, or inhabitants of different planets . . . THE RICH AND THE POOR.”

Cuomo’s “two cities” imagery was a poke at Reagan, turning one of his favorite lines against him. In almost every speech he gave, it seemed, Reagan would refer to America as “a shining city upon a hill,” meaning an example for the rest of the world. Reagan got that from the Puritan preacher John Winthrop (though probably not directly). What Winthrop had in mind was a moral example, but the metaphor works at many levels.

But today two cities are not enough. Today’s politicians require three cities in order to describe our economic predicament: the rich, the poor, and the stars of the show—the middle class. Presidential candidates across the political spectrum agree that the middle class should be the focus of our concern, from Ted Cruz (“Tragic: America’s middle class is headed in the wrong direction”) to Hillary Clinton (“The economy is not working for middle-class families”).

But who is middle-class? Notoriously, Americans tend to define “middle-class” or “middle-income” as whatever income bracket they themselves are in. A Wall Street Journal/NBC News poll two years ago found that people who made less than $30,000 annually believed that they were “middle-income”—and so did people who made more than $100,000. (To be sure, there's a difference between middle-income and middle-class. Class can be defined by lifestyle, social attitudes, and so on. But this poll was explicitly about money, as is the election. No politician is promising the voters a martini and plaid pants.)

Listening to the candidates’ rhetoric, almost every voter in the country could be forgiven for thinking that he or she would benefit from whatever re-distribution of wealth and income the candidate is promising. This is the ambiguity, if not dishonesty, at the heart of Cuomo-ism: Is a politician talking about taking from someone else and giving to me, or taking from me and giving to someone else? And if the answer is “Neither—I’m talking about economic growth for everyone,” then what does that have to do with the specific problems of the middle class?