... For generations historians have asked why there has never been a major socialist movement in American politics—at least not compared with Western European democracies, where socialist parties have often held power or exerted decisive influence. In scholarly circles, the very question—“Why is there no socialism in the United States?”—first posed by the German sociologist Werner Sombart in 1906, has been asked so often it has become a cliché.
To many scholars, the question lost relevance after communism fell in Eastern Europe and the Western European socialist parties abandoned their statist agendas for American-style platforms of regulating capitalism and correcting its excesses. Yet since the Great Recession, young intellectuals have been rediscovering Marx, and campus politics, fairly left wing to begin with, have veered into ever more radical terrain as movements like Occupy Wall Street have made the battle between the 1 percent and the 99 percent the front line of debate. This resurgence of radicalism—coupled with the excitement Sanders has spawned—has made Sombart’s age-old question newly germane.

The “Why no socialism?” query has many answers. Sombart wrote that “on the reefs of roast beef and apple pie, socialistic Utopias of every sort are sent to their doom.” The proletariat here in America lived too well to gamble their stake in the status quo. Other historians, studying social mobility, concluded that while Americans might not really have had more opportunities to advance economically than Europeans, they perceived themselves to have such opportunities—and that those perceptions tamped down any revolutionary desires. Alternately, Louis Hartz argued that because the United States, unlike Europe, lacked a feudal history and the rigid class system that followed, its citizens never developed the class consciousness necessary for a robust socialist movement. Daniel Bell has also pointed to the incorrigible utopianism of socialist thought, which kept its followers from accepting the give-and-take that American politics has always demanded.

Finally, some historians have said that Sombart’s was, in essence, a trick question: After all, there has in fact been socialism in the United States. Although never as influential as their European counterparts, American socialist parties won local races in scores of cities in the late 19th and early 20th centuries and elected the occasional congressman as well. Debs, as their most famous presidential standard-bearer, helped bring the movement’s ideas into the mainstream. It’s fair to say that insofar as socialism has enjoyed success in the political arena, Eugene Debs was as responsible as anyone. It makes perfect sense that Sanders should claim him as a hero....

In the end, the most radical ideas espoused by Debs and his fellow socialists—the abolition of capitalism and its replacement with a planned economy—never came to pass. But more targeted reforms they advocated proved popular and became national policy. It’s here that we find one final answer to the “Why no socialism?” question: While our two-party system has rarely made room for long-lasting third parties, it has proven flexible enough to incorporate those parties’ best ideas. Reforms such as ending child labor, making taxation progressive and funding public works were championed by socialists but quickly came to be understood as liberal ones.

 The same phenomenon seems to be happening today. Sanders, an independent, is not running on a third-party ticket as an actual socialist, even though there is still a Socialist Party that nominates candidates for president. (The last one to make some news was the well-known anti-Vietnam War activist David McReynolds, who appeared on the infamous butterfly ballot of 2000 and cost Al Gore 2,908 votes.) Sanders doesn’t want to cost Democrats the White House, as Ralph Nader arguably did in 2000, and do harm to his progressive causes—he wants to push the party instead to embrace his beliefs. ...