BARACK OBAMA spent his first campaign for president explaining why he was no socialist. Bernie Sanders, the out-of-nowhere candidate who has constituted an unexpected challenge to Hillary Clinton, bravely embraces the label. Yet while Mr Sanders has built his campaign on a jeremiad against wealth inequality and corporate greed, he isn’t, properly speaking, a socialist—or even a democratic socialist. The better term encapsulating Mr Sanders’ positions is “social democrat”, a label that jibes with his rather mainstream embrace of “private companies that thrive and grow in America” and belief that “the middle class and the working families who produce the wealth of America deserve a fair deal”. To clarify matters, Mr Sanders flatly disavows the very heart of socialism as defined by Karl Marx: “I don’t believe government should own the means of production”, he says. So socialists dreaming of sweeping government takeovers of industry and the abolition of private property may have to recruit another candidate. Mr Sanders will give you guaranteed health care, make college free and boost your hourly wage to a minimum of $15, if he can assemble a coalition to do all those things, but he’ll let you keep your house and your dog and will not seek to undermine the bourgeois institutions of marriage, family or religion. He will not take your babies at birth and raise them collectively in dormitories.

As politically far-fetched as his proposals might be, then, Mr Sanders’ views correspond to only a small portion of the socialist programme advocated by Karl Marx in his Communist Manifesto and are a far cry from Marx's vision of a stateless communist society he posits would follow. Mr Sanders would raise income taxes and lower the exemption on estate taxes from $5.4m to $3.5m, but he calls for something far less radical than the “abolition of all rights of inheritance”. (Just two decades ago, when Hillary Clinton’s husband was president, the exemption was a much less generous $600,000.) There is no doubt that the Vermont senator’s positions are to the left of those of his main rival. But even in view of the recent poll showing that 43% of caucus-going Democrats in Iowa associate themselves with socialism, it’s worth considering why Mr Sanders would tag himself with such a fraught political label. We are only one short month away from Super Tuesday, when Democrats in the South are likely to look less kindly on a self-avowed socialist.

Yet in one important sense, the Sanders campaign and its supporters have lifted a page right out of Karl Marx’s 1848 handbook. In chapter 2, “Proletarians and Communists”, Marx responds to objections from communism’s critics who lament the abolition of a number of sacred capitalist values. Here is his deepest rejoinder: “Your very ideas are but the outgrowth of the conditions of your bourgeois production and bourgeois property, just as your jurisprudence is but the will of your class made into a law for all, a will whose essential character and direction are determined by the economical conditions of existence of your class”. Every objection to communism is tainted by its ineluctably compromised source, Marx suggests: a mind that was reared on a steady diet of capitalism. Just a fish cannot see the water he swims in, a capitalist critic of communism cannot fathom the illogic and corruption of the system that defines his personal, political and economic relations.

Marx then asks rhetorically: “Does it require deep intuition to comprehend that man’s ideas, views, and conception, in one word, man’s consciousness, changes with every change in the conditions of his material existence, in his social relations and in his social life?” With a consciousness rooted in a particular web of economic relationships, a critic of communism therefore lacks the perspective to think objectively about his society or how it might be revolutionised. (The idea is intriguing, though paradoxical: how could Marx see beyond his present economic arrangement? He, after all, is a baby of capitalism too. It is hard to see how new social relations could be forged without imagining them, yet an imagination nurtured by capitalism is, according to Marx, blinded to radical change.)

Listen then to Mr Sanders responding to a sharp critique of his campaign offered recently by the editorial board of the Washington Post. On CNN, Mr Sanders had this to say: "I am not greatly beloved by the economic establishment, by Wall Street, by the big money interests, or by the major media of this country including the Washington Post”. And in an oft-heard trope from Sanders supporters, a post at Alternet dismissed the Post’s critique as “establishment gatekeeping”. The editorial “is just another example of this type of dismissive establishment ideology policing”. It might be “helpful to the Sanders campaign”, the writer speculates, that “an oligarch-owned newspaper bashing your every proposal at every turn”.

What Mr Sanders and his supporters do not offer is a persuasive refutation of the Post’s main arguments: that the “evolution and structure of the world economy, not mere corporate deck-stacking”, accounts for “many of the big economic challenges the country still faces” and that Mr Sanders has thus far failed to explain how he will pay for all of his bold proposals. Pushed for details on how to pursue solutions to widening wealth inequality, Mr Sanders reverted to a statement of the problem. And he explains away endorsements of Mrs Clinton as more mainstream thinking: “We are taking on the economic establishment, we’re taking on the political establishment and, with all due respect, we are taking on the media establishment”.

Even if he scores victories in Iowa and New Hampshire, Mr Sanders’ momentum will be short lived unless he does a better job of defending the plausibility of his glittering platform. Faced with legitimate critiques, Mr Sanders will need to do better than repeat the facile claim that his critics are just unable to see beyond their moneyed, mainstream perspectives.