Thirteen million Americans voted for Bernie Sanders in this year’s Democratic presidential primaries—two and a half times the combined general election votes for all Socialist Party of America presidential candidates, ever—and hundreds of thousands volunteered for Sanders’ campaign. This is an astounding success for a socialist candidate in America. But the campaign is over. What follows?

Harold Meyerson, writing in The American Prospect, argues that “Sanders’ campaign didn’t create a new American left. It revealed it.” The Sanders’s campaign, however, has not consolidated that new left—and, given a presidential campaign’s focus on short-term voter mobilization, it probably could not have done so. Meyerson writes:

It’s not that the Sanders campaign itself has incubated some kind of permanent left formation…Leaders of unions, community-organizing groups, minority organizations and student groups, prominent environmentalists and Sanders activists, precinct walkers and online campaigners—some longtime allies, some total strangers to one another—are “all in one large, shifting conversation,” in the words of one such leader, to figure out how to build the Revolution once the Sanders campaign is done.

That conversation seems to be focused, for now, on building organizations, but it ought to move, sooner or later, to reflecting on motives and ideas as well. Meyerson asks: “Who are all these people who now not only flock to Bernie’s banner but deem themselves socialists? What do they even mean by socialism?” He points out that public opinion polls have registered astonishing numbers of Americans who describe themselves as socialists (around 30 to 40 per cent of Democratic primary voters, in some recent polls) but have not asked “this newly hatched brood to define what they mean when they call themselves socialists.” Patching together a plausible answer to the unasked question, he points out that Sanders-style socialists “don’t counterpose socialism to a militant liberalism” and that they “mainly have in mind the social democratic policies—a decent welfare state, more power for workers, and diminished devotion to the gods of the market—of Western European nations.” Such a political stance is not entirely new in America. As Meyerson notes, American politics has included “the functional equivalent” of a European social democratic movement; as long-time democratic socialist leader Michael Harrington once wrote, the American labor movement and its allies (like the early-1960s civil rights movement) have at times served as an “invisible” movement for social democracy.

If the Sanders campaign has, as Meyerson puts it, “revealed” what was previously invisible, then it would seem that something has changed not only for the public at large but also for the members of that newly-visible American social democratic current. If a movement is invisible, its members are not aware that they are members of a movement. They do not know the coherence that their efforts can have or the trouble they are likely to encounter. They do not know that they have a history from which to learn. Perhaps, at least dimly, those things have come into view for some Americans who had not noticed them before.

One valuable thing, thus, that could follow from Sanders’s campaign would be a new moral or intellectual self-awareness among the members of the American democratic left. It is not just that Sanders’s supporters have not told pollsters what they mean by “socialism”: many of them probably are not sure yet what they mean. (Sanders himself, frankly, has not been much help in this regard: even in the November 2015 speech at Georgetown University in which he explained what “democratic socialism” means to him, Sanders was much better at saying how he would foster social equality than at saying why he would do so.) The frenetic bustle of a presidential campaign needs to be followed by patient organizing if it is to yield new or stronger organizations; likewise, a campaign needs to be followed by patient reflection on the part of at least some of its supporters if it is to lead to new or better thinking.

Here, then, is a small gift for “newly hatched” American social democrats: a short reading list surveying the often-unnoticed American social democratic tradition. Taken together, these half-dozen books sketch a lineage; they suggest the characteristic features and challenges of a political movement that has all too often been invisible to itself. Reading them would not be a bad start for those Sanders supporters who want to reflect on what they have begun.

Karl Marx has no monopoly on serious left-wing economic thought. There are alternatives: the work of a Depression-era immigrant New Yorker, for example, provides a classic social democratic account of economic life. A Hungarian exile from fascism who did his most important writing in Vermont and Manhattan, Karl Polanyi developed an economic theory that reads like a twentieth-century rewrite of Aristotle’s Politics. In The Great Transformation (1944), Polanyi argues that political institutions and political decisions gave rise to, and can reign in, the modern market economy. The “great transformation” of the nineteenth century—the detachment of market economies from social or civic purposes—was a political decision, Polanyi argues, and thus can be reversed, or moderated, through politics. Reforms, like those of the New Deal, are socialist because they aim “to transcend the self-regulating market by consciously subordinating it to a democratic society.” Egalitarian policies, in other words, are valuable not because they raise standards of living but because they make possible a humane community. Keeping the market subordinated to democracy may be harder than Polanyi expected; nevertheless, his work frames the project that has occupied socialists like Sanders ever since.

While Polanyi wrote The Great Transformation, thousands of members were resigning from the Socialist Party of Eugene Debs and Norman Thomas to support the New Deal and to build something like a labor party within and alongside the Democratic Party. The most prominent intellectual among the ex-Socialists of the 1930s and 1940s was the Protestant theologian (and Polanyi’s Morningside Heights neighbor) Reinhold Niebuhr. In The Children of Light and the Children of Darkness (1944), Niebuhr makes a social democratic case for, and critique of, American democracy. The Lockean liberalism that influenced the American founders, Niebuhr writes, is naïve when it denies that we need protection against one another’s ambition and greed, and shallow when it ignores the human quest for community and “meaning.” Marxism is right to challenge capitalism, but just as naïve as liberalism when it suggests that a revolutionary government poses no dangers of its own. Those ideologies try to solve the problem of property “once for all,” but democracy, especially when it incorporates a spirit of “religious humility,” expects imperfection and requires continual reform. Democratic institutions are permanently necessary because of “man’s inclination to injustice”—and that, Niebuhr argues, is precisely why democratic principles should be extended to the economic sphere.

If Polanyi provides an economic theory for social democrats and Niebuhr a moral theory, Bayard Rustin offers a strategy. A longtime aide to labor leader A. Philip Randolph (another ex-Socialist of Niebuhr’s generation), the architect of the 1963 March on Washington, and an advisor to Martin Luther King, Jr., Rustin did as much as anyone to shatter the somnolence of the 1950s. Rustin’s 1964 essay “From Protest to Politics”—republished, along with other valuable essays, in Time on Two Crosses (2003)—is the classic statement of what Rustin and his friend Michael Harrington called the “realignment” strategy: if labor unions, civil rights organizations, and middle-class liberals could forge a durable alliance, bridging movement “protest” and ordinary electoral “politics,” Rustin wrote, they could reorient the Democratic Party toward an agenda of radical reforms.

The escalation of the Vietnam War broke up Rustin’s coalition (and his collaboration with Harrington), showing—not for the first or the last time—how fragile a broad reformist coalition is likely to be, and how far from certain social democratic victories are. The idea of a labor-community coalition with an inside-outside approach survives today in efforts like Fight for 15 and the Working Families Party, but despite occasional, mostly marginal, reform projects like these, the past forty years or so have seen inequalities widen and solidarities erode. No writer shows half so well what it has felt like to be on the democratic left in America during these decades as has Thomas Geoghegan in The Secret Lives of Citizens (1998). “When I was thirty and sick of D.C.,” he writes, “I thought: ‘Oh, go! Just pick out a city and be a citizen of it.’” Geoghegan picks Chicago, “our political city,” but—between Washington gridlock and busted unions and busted cities—being a citizen is not easy in the Carter-to-Clinton era. Geoghegan’s pensive memoir fits together noodle shops, planning commission meetings, votes cast and votes missed, the pleasures of the civil service, Chicago mayoral races, community organizing, a visit to night court, graphs of pay inequality. Geoghegan—a labor lawyer whose other books have described the travails of American unions and the advantages of European left policies—knows the frustration of trying to be a citizen in an uncitizenly time, but refuses to abandon the dream of seeing “the whole republic in a single glance.”

Throughout the sad era on which Geoghegan muses, Michael Walzer has been the principal intellectual voice of American social democracy. A long-time editor of Dissent and a prolific political theorist influenced by the works of Polanyi’s friend R.H. Tawney and by Dissent co-founder Irving Howe (who moved from being a left-wing critic of Niebuhr toward his own variety of social democracy), Walzer advocates “connected criticism,” a style of argument that operates inside the shared “moral culture” of the critic and the critic’s audience—recalling both the Biblical prophets and the American community organizing maxim “Start where the people are.” In Politics and Passion (2005)—the best introduction to his political thought—Walzer challenges the American tradition of Lockean individualism from within, revealing social democratic possibilities in American political culture. “Standard liberal theory,” he argues, makes “the struggle against inequality more difficult than it should be,” but liberal theory can incorporate a more realistic assessment of power and inequality, of the importance of the memberships to which we do not express our consent, of civil society’s need for support from the state, and of the role of passion—or “impassioned reason”—in helping us to answer the fundamental political question: “Which side are you on?”

Walzer’s “connected criticism” is typical of social democratic thinking. Nevertheless, it is no secret that American democratic leftists—Sanders included—admire European, and especially Scandinavian, social democratic achievements. In The Primacy of Politics (2006), Sheri Berman shows why the American left often gazes longingly abroad. Drawing on Polanyi, Berman looks backward at the emergence of a new reformism in northern Europe between the 1890s and 1930s. While fascists of that time invented a new authoritarian nationalism, social democrats sought a democratic way to revive “politics” (in Aristotle’s sense: public decisions about shared concerns). The welfare state, a mixed and regulated economy, legal backing for trade unions: these policy innovations belied the economic determinisms of both classical liberalism (The market is always right!) and Marxism (You can’t reform capitalism!). At the same time, the cross-class coalitions forged by social democratic parties suggested that there is more to politics than class conflict. Most important for American readers is Berman’s sense that—unlike in America, where even supporters of social democratic policies have tended to ignore social democratic ideas—social democracy has been, at its best, an intellectual tradition: neither “watered-down Marxism nor bulked-up liberalism, but…a distinctive ideology…all its own.”