Open this photo in gallery R.J. Pettersen, right, and Miriam Callahan help organize different events for the Democratic Socialists of America to reach out to the community about issues they care about. JACKIE MOLLOY/The Globe and Mail

In a quirk of Manhattan geography, the heart of the U.S. socialist revival is located just down the block from a temple of U.S. capitalism.

The Democratic Socialists of America (DSA) occupy a cramped, bare-bones office on the seventh floor of a tired-looking commercial building, an infielder’s throw away from the massive neo-Renaissance fortress of the Federal Reserve Bank of New York. The contrast between the two abodes tells you everything you need to know about the traditionally fringe status of the left in U.S. politics.

But that is shifting. The DSA, an umbrella organization that spans viewpoints ranging from Scandinavian-style socialism to outright Marxism, has emerged over the past two years as one of the fastest-growing forces on the American political scene. Its dues-paying membership has swelled more than sevenfold since the election of Donald Trump, and now stands at 52,000 people.

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The organization is seeking to make an impact in next week’s midterm elections, when 49 DSA members will be running for offices across all levels of government. They include Alexandria Ocasio-Cortez, the charismatic bartender-turned-politician, who this summer staged a stunning upset of a long-time incumbent in the race for the Democratic nomination in a New York congressional district.

Open this photo in gallery Alexandria Ocasio-Cortez speaks at a rally against Supreme Court nominee Brett Kavanaugh, in Boston, on Oct. 1, 2018. Brian Snyder/Reuters

“Our strategy focuses on what we have, which is volunteer energy, not money,” says Maria Svart, national director of the DSA. Many voters, especially millennials, are fed up with both Republican and Democrat clichés, especially after years of deteriorating standards of living for many U.S. workers, she asserts.

She points to the passion unleashed by the 2016 presidential campaign of left-leaning Bernie Sanders as evidence that socialism is gaining mainstream appeal. The numbers, at least among the young, bear her out: A Gallup poll in August showed Americans under the age of 30 are more positive about socialism than capitalism.

In a telling indicator of the left’s growing mainstream appeal, the White House’s Council of Economic Advisers produced a report in October lambasting the costs of socialism. The report is less than completely convincing – one of its key exhibits trumpets the relatively low cost of owning a pickup truck in the United States – but the mere fact the CEA produced the document shows the concern in some quarters that socialism is gaining ground.

To be sure, many DSA demands don’t seem particularly radical from a Canadian perspective. Its three current priorities – electing leftists to office, building strong unions and delivering a single-payer, medicare-for-all system – would appear utterly mainstream north of the border.

Open this photo in gallery A pro-medicare button is pinned to the jacket of Colette Swietnicki, a member of the activist group Uptown Progressive Action, at the DPA canvassing event in Manhattan. JACKIE MOLLOY/The Globe and Mail

But the deeper significance of the DSA lies in its capacity to shake up the U.S. political duopoly. “We saw an explosion in membership numbers the minute Trump went on the news and said he was winning,” Ms. Svart says. She says many of those new members are disappointed, not just in Republicans, but in “Wall Street Democrats” such as Hillary Clinton, who befriend corporate interests and are “completely uninterested in what working-class people have to say.”

What is needed, she says, is a voice on the left that can speak up for ordinary people ground down by the system. “That’s the anger Trump is tapping into. The last 40 years have been an onslaught against working people in this country. Productivity has been going up, but wages have been going down.”

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The DSA wants to build institutions – notably strong unions – that can punch back against inequality. It is completely independent from the Democratic Party, but often chooses to work within the larger group. For instance, it campaigned for Mr. Sanders, who describes himself as a democratic socialist, although the Democratic Senator from Vermont is not a member of the DSA.

The question is whether the enthusiasm tapped by the Sanders campaign of 2016 will evaporate in the current red-hot U.S. economy. Larry Sabato, head of the Center for Politics at the University of Virginia, says he sees no evidence that voters, outside of a few big coastal cities, are yearning for a more left-leaning platform. “Let’s be honest,” he says. “The media creates a trend out of two or three cases.”

Others are more positive. Joseph Stiglitz, a Nobel-winning economist, argues a tilt to the left by Democrats could galvanize the majority of citizens who don’t bother to vote. Adam Tooze, a professor of history at Columbia University, says the DSA could become to Democrats what the Tea Party is to Republicans – a small group that wields disproportionate influence by punishing those within the larger party who don’t agree with it.

For now, Ms. Svart says the DSA is focused on grassroots action on issues from teachers strikes to tenants’ rights. “Elections aren’t the be all and end all,” she says. “We’re trying to do the work door-to-door, to get the message out there beyond lefty reading groups.”

Open this photo in gallery Five-year-old Raul Ortiz and his brother Jaden, 3, speak in Manhattan with Miriam Callahan of the Democratic Socialists of America. Raul is filling out a postcard to Steven Corwin, CEO of New York-Presbyterian Allen Hospital, in an attempt to help stop the potential shutdown of the psychiatric unit. JACKIE MOLLOY/The Globe and Mail

Open this photo in gallery A DSA member carries a clipboard of postcards at the Manhattan canvassing event. JACKIE MOLLOY/The Globe and Mail

One example takes place on an overcast Saturday morning, when half-a-dozen DSA members meet at a farmer’s market near the northern tip of Manhattan to protest plans by a local hospital to close its psychiatric unit. The closure, which would open space for a more lucrative spinal clinic, would force local residents to travel long distances for psychiatric care.

One of the DSA members is R.J. Pettersen, a smiling, bearded, 31-year-old educational administrator, who joined in August, 2017, after being appalled at the President’s reaction to the unite-the-right riots in Charlottesville, Va. “Hi, sir, have you heard about the plans to close Allen Psych?” he asks a passerby. After discussing the issue, the man agrees to write a message on a preprinted postcard, which the DSA will deliver to the hospital’s chief. The postcard also contains an invitation for the sender to join DSA as well as stay involved via e-mail.

Over the next couple of hours, dozens of other people also agree to sign the cards. In time, the hope is that this and similar campaigns will introduce the DSA to people, build membership and begin winning victories on local issues. “We’re trying to build a community power base here,” Mr. Pettersen says. “And we’re succeeding.”