The list

Jon Stewart and Stephen Colbert

Van Jones

Paul Krugman

David Graeber

Elizabeth Warren

Rachel Maddow

Matt Damon

Congressman Keith Ellison

Sonia Sotomayor

Noam Chomsky

Katrina vanden Heuvel

Markos Moulitsas

Cornel West and Tavis Smiley

Cecile Richards

Danny Glover

Angela Davis

Glenn Greenwald

Tim Robbins

Michael Moore

Bernie Sanders

Don't dare say the "S" word around Barack Obama - or his advisers. In March 2009, a New York Times reporter asked the US president whether his spending priorities might suggest that he was a socialist. "The answer would be no," Obama replied. However, following a discussion with his ultra-cautious, centrist White House aides, a panicked president called the reporter back to add, defensively: "It was hard for me to believe that you were entirely serious about that socialist question . . . It wasn't under me that we started buying a bunch of shares of banks."

The president proudly declared that he had been "operating in a way that has been entirely consistent with free-market principle" and that "some of the same folks who are throwing the word 'socialist' around can't say the same".

Obama, of course, isn't a socialist - except in the fevered imagination of far-right opponents such as the Republican presidential candidate Newt Gingrich, who titled a recent book of his To Save America: Stopping Obama's Secular-Socialist Machine. Over the past three years the US president has disappointed not just leftist radicals and card-carrying socialists, but even the mildest liberals, having refused to push for a bolder, European-style, single-payer reform of the US health-care system and having signed off on spending cuts that, in his own words, will result in "the lowest level of domestic spending since Dwight Eisenhower was president". To the New York Times columnist Paul Krugman (see page 26), Obama is a "moderate conservative"; to the former Reagan policy adviser Bruce Bartlett, he is the "Democrats' Richard Nixon".

Authentic leftists - either socialists or social democrats - are few and far between in the United States. There is just one self-described socialist sitting in Congress: the independent senator from Vermont, Bernie Sanders (see page 33). In fact, the US is the only advanced, industrialised nation whose political system remains bereft of a large, mainstream, avowedly social-democratic political organisation such as our own Labour Party or the French Socialist Party. "Why is there no socialism in the United States?" the German sociologist Werner Sombart famously asked in the 1880s. More than a century later, the question stands - and still has no adequate answer.

Signs of life

In his acclaimed new book, American Dreamers: How the Left Changed a Nation, the US historian Michael Kazin argues that socialists and progressives have had a huge transformative effect on American culture, helping to boost the rights of women, racial minorities and

homosexuals. Yet even Kazin concedes that the US left has lacked impact: it has never succeeded in building durable institutions or movements, winning elections, or enacting its economic programmes. And the present era, he argues, could be described as "a nadir of the historical left". The latest polls show that only one in three Americans has a positive reaction to the word "socialism"; one in five Americans self-identifies as "liberal".

Yet all may not be lost. There are flickering signs of life on the US left. An energised Congressional Progressive Caucus, led by Keith Ellison (see page 29), is now the single biggest Democratic bloc on Capitol Hill. In recent months, the CPC has helped push Obama to the left on job creation. In Wisconsin, public-sector unions mobilised tens of thousands workers who took to the streets to protest against Republican plans to restrict collective bargaining rights.

Meanwhile, the Occupy movement, which erupted on Wall Street in September 2011, has spread across the United States - from Arizona to Alaska, from California to Colorado. Astonishingly, a Pew Research Centre poll released in mid-December showed that 44 per cent of Americans support Occupy Wall Street and just 35 per cent are opposed to it.

What next? What forces can these nascent, populist left-wing movements call on for support in the worlds of politics, economics, academia and the media? We've profile 20 leading American progressives (see list above), from a range of backgrounds, who have been at the forefront of efforts to defend not just liberal, but left-wing, social-democratic ideals. Some of them are well-known names; most of them have little to do directly with the Democratic Party; all of them are defiantly and unashamedly partisan.

As Markos Moulitsas, founder of the Daily Kos blog, once said: "I am a progressive. I make no apologies."