In autumn 2003, a new class called 'What's Left? The Politics of Social Justice' began at Harvard University. The visiting lecturer played a video of a Newsnight interview with Tony Blair in the run-up to the 2001 election. In the clip, Jeremy Paxman asked the then prime minister six times whether the gap between rich and poor mattered - and six times he dodged the question. "It's not a burning ambition for me to make sure that David Beckham earns less money," was one response.
The lecturer was Ed Miliband, then a 33-year-old special adviser in Blair's government, on a sabbatical in the US. Inequality bothered Miliband much more than his boss. In June 2013, the Institute for Fiscal Studies concluded that between 1997 and 2010, "Those right at the top saw their incomes increase very substantially with the result that... overall inequality nudged up slightly." A friend of Miliband's from his Harvard days told me that the failure to tackle the gap between the rich and the rest was "a key source of his dissatisfaction with Blair and New Labour" during this period.
More than a decade later, the leader of the Labour Party believes that "tackling inequality is the new centre ground of politics", to quote from his Hugo Young Lecture on 10 February. His closest adviser, the academic and peer Stewart Wood, leads the charge on inequality inside Miliband's office. "Ed's concern to stop Britain continuing down the path of growing inequality, to the detriment of social justice and our economic health, will be central to any government that he leads," Wood tells me.
But aren't all Labour leaders - with the exception of Blair and maybe Gordon Brown - concerned with the gap between rich and poor? Perhaps. However, the difference is that inequality is no longer a niche issue.
Forget Occupy Wall Street - how about the new mayor of New York, Bill de Blasio, elected on a populist pledge to tackle the Big Apple's "tale of two cities"? Or the new darling of the US Democratic Party, Senator Elizabeth Warren of Massachusetts, who has called for a minimum wage hike to "stop income inequality in America"? Or even the US president? In a speech in December, Barack Obama called the income gap "the defining challenge of our time".
Listen also to the words of the Pope. "While the earnings of a minority are growing exponentially, so, too, is the gap separating the majority from the prosperity enjoyed by the happy few," the pontiff wrote in November. Then there's the IMF, which said in February that inequality hinders growth.
Miliband invoked both de Blasio and the Pope in his Hugo Young Lecture; he often cites their names and Warren's in private as well. "Whose recovery is this?" has replaced "Too far, too fast" as the economic mantra of choice in his office. Miliband believes the paradigm has shifted. The public is fed up with the rise and rise of the super-rich - the one percenters - at the expense of everyone else. Consider the polling: 74% of voters believe the gap between rich and poor is widening (ComRes); 60% say the Autumn Statement was good for "rich people", compared to just 21% who say it was good for "people like me" (Ipsos MORI); and a majority of voters (64%) think company bosses shouldn't be paid in excess of ten times more than their lowest-paid employees (Survation).
Yet, between 1985 and 2008, the top 10% went from receiving incomes that were eight times higher than the bottom 10% to incomes that were 12 times higher. According to the High Pay Centre, the chief executives of Britain's biggest companies earned more money in the first three days of the year than the average worker will make over 12 months.
On 10 March, Capital in the 21st Century, by the French economist Thomas Piketty, is published in English. Described as "one of the watershed books in economic thinking" by the World Bank's Branko Milanovic, it argues that the main driver of soaring inequality - the tendency of returns on capital to exceed the rate of economic growth - is hard-wired into modern capitalism and threatens to undermine modern democracy. The author's solution? A global wealth tax.
Such utopian thinking won't help Miliband but to pretend that Labour policies - such as a levy on bankers' bonuses, a 50p top rate of tax, a mansion tax and a living wage - won't make a dent in income inequality is disingenuous. Wood, a fan of the book, says: "We must respond to [Piketty's] challenge with ambition and imagination, not with pessimism." Labour, he tells me, "needs to set itself the task of reforming the way our economies work so that higher productivity and lower inequality go together".
This isn't just about economics. The politics matter, too. Pledging to tackle inequality - within the rubric of "Whose recovery is this?" - helps Labour neutralise the positive Tory narrative of "Growth is back". Crucially, it offers Miliband his own brand of progressive populism to challenge the right-wing, anti-welfare populism of the Conservatives. This is the Inequality Moment. Yet the Tories, with their historic aversion to any mention of the "I" word, will struggle to answer the question: "Whose recovery is this?" Miliband's calculation is that voters won't.
Mehdi Hasan is the political director of the Huffington Post UK and a contributing writer for the New Statesman, where this column is crossposted