Bernie Sanders has tapped into a potent mix of skepticism and hopefulness, especially among young voters, in his run for the White House. PHOTOGRAPH BY JOHN MINCHILLO / AP

From up close, election campaigns appear to be messy and contingent affairs that pivot around individual characters and tactics. Did Donald Trump make an error, after all, in skipping last week’s Fox News debate? Can Marco Rubio handle the spotlight? Will Hillary Clinton shift further left to counter Bernie Sanders?

If you step back a bit, though, all of the players look more like pieces in a board game, whose rules and layout are predetermined. As Karl Marx famously remarked, in “The Eighteenth Brumaire of Louis Napoleon,” “Men make their own history, but they do not make it as they please; they do not make it under self-selected circumstances, but under circumstances existing already, given and transmitted from the past.”

Going into the 2016 Presidential election, our economic inheritance is forty years of income stagnation and rising inequality, which culminated, in 2007 and 2008, in a global financial crisis and a government rescue of bankers and other financial interests. Yes, this bailout has been followed by half a decade of modest G.D.P. growth and strong job growth, but the narrative of inequity, unfairness, and frustrated expectations remains fixed in the public consciousness.

As the Financial Times commentator Martin Wolf pointed out on Wednesday, Latin American-style income distribution leads to Latin American-style politics—populism of the left and the right. Over the past few years, in Europe, we have seen new anti-establishment parties on the left, such as Syriza, in Greece, and Podemos, in Spain, enjoy great success, particularly among young voters. Older leftist groups, such as the Left Bloc, in Portugal, and the Bennite wing of the British Labour Party, have also made big gains. On the right, traditional conservative politicians have been outflanked by more extreme voices, such as Austria’s Freedom Party, Greece's Golden Dawn, the United Kingdom Independence Party, and France’s National Front.

On this side of the Atlantic, in the years immediately following the crash and the bailout, Occupy Wall Street and the Tea Party emerged. Both movements reflected a growing alienation from regular politicians, who were widely seen as too tight with corporate interests. Neither group was powerful enough to create a new political party or to seize full control of an old one, but they both left their mark. Now we have Bernie Sanders and Donald Trump, who are tapping into many of the same popular sentiments.

This new populism, as it might be termed, connotes a deep suspicion of political, corporate, and media élites; an eagerness to mobilize people who are new to politics; and a willingness to embrace policies that have long seemed verboten. On the right, this has meant proposals to crack down on immigrants, Muslims, and outsiders of all kinds. On the left, it has meant demands to downsize big banks, crack down on tax-dodging multinationals, shift to a much more progressive tax system, and get serious about curbing carbon emissions.

Sanders says that he would take all of the latter steps. But what really sets him apart isn’t his policy platform, which can be fairly described as shifting the United States toward the Scandinavian model of social democracy more rapidly than Clinton and other Democrats would; it’s his fiery rhetoric. In calling for a “political revolution,” attacking the “billionaire class,” and embracing the label “democratic socialist,” Sanders is using language that has never been heard before in a Democratic Presidential primary. (Socialists such as Eugene Debs and Norman Thomas have run for President in the past, but on the ticket of the Socialist Party.)

Some political analysts seem taken aback that Sanders’s leftist language is resonating broadly among Democrats, particularly young ones, but they shouldn’t be surprised. A recent O.E.C.D. study showed that, between 1975 and 2012, nearly half of all the pre-tax income growth in the United States went to the richest one per cent of households. Another study, by the economists Emmanuel Saez and Gabriel Zucman, showed that the richest 0.1 per cent of households own almost a quarter of the country’s wealth, which is more than the bottom ninety per cent of households.

Thanks to the efforts of Sanders and others, such as the French economist Thomas Piketty, disturbing facts like these form part of the mental picture that voters, and particularly young voters, now have of the world. Partly for this reason, some old political labels are being reassessed. In a January poll of likely voters in the Iowa Democratic primary, forty-three per cent of respondents described themselves as “socialist.” And it isn’t just Iowa. A 2011 study by the Pew Research Center found that forty-nine per cent of millennials—defined as Americans between the ages of eighteen and twenty-nine—view socialism favorably, compared to forty-three per cent who view it unfavorably. Asked about capitalism, forty-six per cent of the respondents said that they viewed it favorably, and forty-seven per cent said that they viewed it unfavorably.

This changing ideological environment is another of the “circumstances” shaping the Democratic contest. It reflects not merely the problems that global capitalism has encountered over the past few decades but the passage of time. The stigmatization of left-wing politicians and left-wing ideas dates back to the Cold War, which ended twenty-five years ago. That was before many Sanders supporters were born. In the absence of the Soviet Union and Mao’s China, the world “socialist” doesn’t have the same connotations that it once did.

So what does it mean, these days, to say that you view socialism positively? In voting for Syriza and Podemos, the Greeks and Spanish weren’t indicating that they wanted to nationalize the means of production or bring back the Comintern. They were rejecting austerity policies imposed by a political system that seemed beholden to bureaucrats in Brussels and bankers in Frankfurt, and they were calling for a return to the Enlightenment ideals of popular sovereignty and popular participation. Something similar is true of Sanders’s supporters. When they attend his rallies and cheer his exhortations to “take back our government from a handful of billionaires,” they aren’t merely endorsing his class-based analysis: they are expressing hope—hope that, even now, at this late stage in the ossification of the American system, political mobilization can change things for the good.

To my mind, the most striking thing about the Iowa poll wasn’t that virtually half of likely Democratic voters embraced the designation “socialist.” It was that eighty-eight per cent agreed that the word “optimist” described them. Among younger Democratic voters, I would guess that the percentage of optimists is even higher. A 2014 Pew Research study of millennials found them “burdened by debt, distrustful of people,” and “in no rush to marry.” But, despite all that, they were “optimistic about the future.”

For all his crankiness, Sanders is tapping into this optimism and providing an outlet for it. Other populist movements do the same thing. The English translation of the word “podemos” is “We can.” Clinton, although she retains a great deal of support in the Democratic Party, has so far failed to inspire the young. As I noted following the Iowa caucus, her response to the Sanders phenomenon sometimes seems to be “No, we can’t.”

Appearing on MSNBC’s “Hardball” on Tuesday night, the former Secretary of State briefly tried to strike a more upbeat note. She said that it was a positive development that so many young people are getting involved in the political process. But then she altered course, warning about the danger of allowing the Republicans to regain the White House. Meanwhile, the host, Chris Matthews, bemoaned the failure of the “kids” to understand the realities of American politics.

If you look at the rise of populism in other countries, you will find that urging people to be realistic is a common reaction from establishment politicians and their supporters. It is a risky response, though. Trotted out too often, or too vehemently, it can make those who rely on it sound suspiciously like one of the “mothers and fathers” that Bob Dylan addressed back in 1964—those people whose “order is rapidly fadin’,” whose “old road is rapidly agin’,” and who, finally, are bid, “Please get out of the new one if you can’t lend your hand.” That, of course, is something no politician wants to hear, especially one who came of age in the sixties.