On November 9, the day after this year’s election, Donald Trump may well join Bernie Sanders as a footnote to U.S. history. But that doesn’t mean that their candidacies will vanish without a trace. In a decade or two, American politics may look as strange to us as the conservative politics of the 1980s looked from the liberal vantage point of the 1960s. And part of the reason will be Trump and Sanders, and what they revealed about the soft underbelly of our political system.

Trump and his followers are regularly denounced as fascist, nativist, misogynist, and racist. “We want him off the stage,” political scientist Peter Dreier declared in August, “and we want his racist followers to know that they represent a tiny sliver of America.” Sanders was dismissed by Clinton backers and Republicans as a “utopian socialist” whose supporters were “naïve idealists.” But such simplistic dismissals overlook something essential about both men’s campaigns—and about the impact they are likely to have.

Leaving aside his bilious nature, his preening self-absorption, and his casual bigotry, Trump represents a tradition of American populism that dates back to the 1880s. So does Sanders. And in America, populist campaigns, movements, and parties have played a vital role: Their ascendancy serves as an early warning signal that the political consensus uniting the country—and the leadership of both major parties—is breaking up. Populist campaigns have prefigured, provoked, and sometimes precipitated political realignments. To understand why the forces unleashed by Trump and Sanders will outlast their campaigns, you have to understand American populism.

There are as many meanings of populism as there are of liberalism and conservatism. Sometimes the term is simply used as a synonym for popularity. Sometimes business lobbies like the Koch-funded Americans for Prosperity borrow populism’s language of anti-elitism to camouflage their self-interest. But there is a political tradition in America that begins with the Farmers’ Alliances of the 1880s and the People’s Party of 1892 (whose adherents coined the term populist) and extends down through Huey Long and George Wallace, to Ross Perot and Pat Buchanan, to the Tea Party and Occupy Wall Street, and finally to Trump and Sanders.

The central feature of all these populist campaigns has been the attempt to champion “the people” against an elite or establishment. But how the people and the elite are defined has changed with the campaigns. The People’s Party represented “the plain people” against the “plutocracy,” Huey Long the “poor man” against the “money power,” Wallace “the man in the street” against “big government,” Trump the “silent majority” against the “special interests,” and Sanders “we the people” against the “billionaire class.”