Shortly after the turn of the 20th century, Werner Sombart, a German sociologist, visited the United States. The monograph he published, in 1906, based on his travels would become a kind of ur-text for American exceptionalism: “Why Is There No Socialism in the United States?”

Read this forgotten classic now, before it expires — so to speak. Come Jan. 20, 2021, Sen. Bernie Sanders (I-Vt.), a democratic socialist, might mark its 115th anniversary by being sworn in as president.

The book’s title is a bit misleading: Sombart wasn’t writing about the absence of an actual socialist system in this country, but the lack of a strong labor-based socialist political movement, akin to what was then a rising Social Democratic Party in Germany.

Sombart, influenced by Karl Marx, thought that capitalism had reached its purest form in the United States and, therefore, the American proletariat should be expected to respond with a commensurately high level of socialist militancy and political consciousness.

It had not done so, he argued, because of the high wages and abundant opportunities U.S. workers enjoyed compared with their European counterparts. “On the shoals of roast beef and apple pie,” he famously explained, “all socialist utopias founder.” Widely shared prosperity bestowed legitimacy on capitalism and discouraged class-based resistance to it.

Which brings us to the question: Why, now, is there socialism in the United States?

Per Sombart’s roast-beef-and-apple-pie aphorism, socialism should be in retreat, because full employment reigns and Americans are more confident than ever about their personal finances, according to a January Gallup poll. And, indeed, socialism is still viewed positively by only a minority.

That minority, however — 43 percent in a 2019 Gallup poll — is up 18 points since 1942, notwithstanding the failure of so many attempted collectivist utopias around the world in the interim. And socialism polls best among the young.

There is obviously more to the story — as Sombart also recognized. U.S. political institutions, he wrote, were uniquely different from those in Europe, in ways that discouraged a working-class party.

Specifically, American two-party electoral politics formed a bulwark against the rise of a socialist party like the one in Germany. Non-ideological, patronage-seeking Republican and Democratic machines (often appealing to different ethnic groups among the heavily immigrant-origin population) co-opted workers and convinced them that their primary identities were those of region or party, not class.

This disadvantaged third parties of all kinds, which usually found themselves absorbed into the two big ones after trying and failing to gain a following.

(Sombart alluded to the impact of slavery, and of its abolition through the Civil War, on partisan affiliation in the United States, though he failed fully to appreciate the role of racism and white supremacy in undermining working-class solidarity.)

This constraint — two disciplined, “gatekeeper” political parties — held up even through the rise of leftists such as Eugene V. Debs, Norman Thomas and Henry Wallace after Sombart’s time.

It has collapsed, however, in the 21st century. First, the Cold War ended, and with it the threat that the Soviets might take advantage of U.S. partisan strife, which had helped to keep Republican and Democratic ideology, and policy, within broad centrist channels.

Then came a series of shocks to the body politic more disruptive than any since the 1960s or possibly the 1930s: trade-related deindustrialization; 9/11 and the “endless wars” in Iraq and Afghanistan; the 2008-2009 recession; cultural change driven by social media; mass opioid addiction.

It was Sombart’s intellectual precursor Marx who wrote of the modern world’s “constant revolutionizing of production, uninterrupted disturbance of all social conditions, everlasting uncertainty and agitation.”

Those words come from the “Communist Manifesto,” which was written in 1848, but they describe almost perfectly the angst that so many Americans feel today.

Even recent prosperity has not fully restored Americans’ previous level of confidence in free-market capitalism, in part because it appears to rest on a shaky foundation of debt, and in part because of growing income and wealth inequality.

The reformism that broadly characterized U.S. politics from FDR through the Obama administration seems to be losing traction. Voters seek protection in the promises of ideologies that last enjoyed currency a few years before President Trump or Sanders were born: “America First” and, yes, democratic socialism.

Instead of two big-tent parties absorbing the fringes, as Sombart described, the fringes are absorbing the parties. The first to go were the Republicans, taken over by Trump. Now Sanders is bidding to take over the Democrats. You might say they are both becoming third parties.

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