Eugene V. Debs, 1918. Photo: Bettmann/Corbis

A dozen years ago, John Edwards, then still the Democratic Party’s fair-haired boy, had a signature catchphrase on the stump to describe the Bush administration’s economic policy. He called it “the most radical and dangerous economic theory to hit our shores since socialism.” That was the nastiest comparison Edwards could come up with — to an extreme and long-dead ideology. The reference worked only because Edwards’s target audience of Democratic-primary voters could all agree socialism was as unworkable and monstrously evil as, well, the Bush economic program.

In a few days, when the three remaining Democratic candidates for president gather in South Carolina for a forum hosted by Rachel Maddow, none will be using “socialist” as a slur. One of them, of course, adopts it as a proud identifier. Bernie Sanders has not turned the Democratic Party socialist — nor even, technically speaking, joined it, choosing to remain nominally independent. But Sanders’s campaign has made socialism relevant to the national political debate for the first time since Eugene V. Debs garnered 6 percent of the vote in 1912. It is looking increasingly likely that the 2016 election will mark a historical turning point in the relationship of socialism to mainstream politics in the United States.

In most democracies, socialism does not connote something horrifying or alien. The United States is unusual among democracies in that it lacks a true mainstream political party with roots in the labor movement. American liberalism developed in the 20th century mostly out of policies implemented by the Democratic Party, which had its strongest base in the South, a deeply segregated, heavily agricultural region with a traditional suspicion of centralized power. The Democrats have never been a labor party; unions have always had to jostle with business for influence. The Cold War further served to identify socialism with communism. But this deep and very American hostility may be breaking down. Recent polls have shown that voters in their 20s think just as highly of socialism as they do of capitalism.

That socialism is no longer a dirty word has freaked out conservatives. As Arthur Brooks of the American Enterprise Institute worried in 2010, “The young sympathizers of socialism today may be the grown-up defenders of socialism tomorrow.” Rand Paul, who prides himself on his hipness, has warned young people to stay away. “I’ve been trying to point out — because I’m on a lot of college campuses, we have a big following in college campuses — that there’s nothing sexy and there’s nothing cool about socialism,” he told Glenn Beck. Oh, socialism might sound cool, and you might impress kids at a party, but eventually you will find yourself facedown in a ditch, or perhaps digging one in a Siberian labor camp. (I’m not kidding. “Only the state tells you what you can do; it’s the most anti-choice economic system,” Paul said. “If you don’t listen, they fine you. If you don’t pay the fine, they imprison you. If you will not listen, ultimately, what has happened in history, and people get mad when I say this, but they exterminate you. That’s what happened under Stalin.”)

Nobody is actually proposing to import Soviet-style communism to the United States. In fact, for a term so freighted with the capacity to inspire its supporters and terrorize everybody else, “socialism” is oddly bereft of any specific meaning. A self-described socialist might endorse government control of industry (the “means of production”), or equal incomes for all, or a “maximum income” above which the government taxes everything, or none of those things. Sanders urges a political “revolution,” but he means the term metaphorically. If you drill down into his platform, it’s mostly the same stuff Democrats support, but more of it — higher taxes, more infrastructure and social spending, tougher regulations on Wall Street. He’s not even demanding economic equality — just less inequality. In the most literal sense, Sanders’s socialism seems hard to distinguish from regular liberalism.

Still, it would be a mistake to dismiss socialism’s new respectability as a mere branding device. Some things exist even though they lack a clear definition. One way to understand socialism in Obama-era America is as a rough left-wing analog to the tea party. These socialists consider the political process fundamentally corrupted by large corporations and harbor suspicions of any policy that relies on, or makes peace with, the profit motive. This idea forms a through-line connecting the left’s objections against the major items of Obama’s agenda. Socialists deemed his health-care reforms deeply disappointing, because they relied on private insurance companies and failed to create a public option to compete with them. They criticized his Wall Street reforms for regulating the big banks rather than breaking them up. And they judged a failure the cap-and-trade law he tried to pass in 2009 and 2010, which compromised too much with energy companies and relied too heavily on market forces. Obama likes to boast that his policies have enabled the private sector to thrive; socialists consider this an inherent problem.

The debate within the Democratic Party can be seen as an indication that socialist thought has risen to challenge the once-dominant liberal creed. Socialists use adjectives like “corporate” and “market” as terms of abuse. Teachers unions and their allies highlight the financial ties between wealthy donors and the education-reform movement as evidence of something corrupt and even sinister.

Naomi Klein, a Canadian writer who rose to prominence as a voice of the anti-globalization movement in the ’90s, has a new documentary based on her 2014 book, This Changes Everything: Capitalism vs. the Climate. Klein argues that any attempt to limit carbon emissions through a market-based system is bound to fail; only a frontal assault on the free market can do the trick. Klein even dismisses Obama’s cap-and-trade failure as a “narrowly dodged bullet.” The only morally legitimate policy she can imagine is one that rides atop a populist uprising that sweeps away any consideration of business interests from the political scene.

Sanders makes iterations of the same case. He waves aside the need to compromise on his policy agenda, asserting that his election would be a transformation of American politics. At the first debate, Sanders argued again and again that his agenda could not possibly succeed unless the people rose up and took on “the big-money interest” or “the billionaire class.”

Like Bill Clinton before him, Obama likes to needle his adversaries by pointing out that the stock market has soared during his presidency. He ridicules conservative fears that he is a socialist — “There’s some folks who just weren’t sure whether I was born in the United States, whether I was a socialist, right?” — and depicts the anger aroused by his agenda among wealthy financiers as irrational and unhinged. Obama and Clinton come from a political tradition that saw the role of government as saving capitalism from itself — a framing Hillary Clinton has also adopted. But Hillary is the first Democratic front-runner in her lifetime whose main competitor for the nomination is a candidate with a very different idea of how to measure success.

Much has been made of the Democratic Party’s new confidence on social issues — its sense that the America of minorities, eggheads, and secular elites has emerged as a cultural majority. Sanders has given voice to a different idea, the conviction that the party can shed its defensiveness on the role of government and evolve into a fully European-style labor party that makes no apologies for potential statist overreach. Clinton remains a shoo-in to win her party’s nomination, and when she does, Sanders may recede as a national figure. But what we are watching right now in the Democratic debates is a genuine clash of ideologies and, perhaps, a pivot in the party’s long-term development. Even in the face of likely defeat, Sanders has brought new life to an old tradition.

*This article appears in the November 2, 2015 issue of New York Magazine.