And yet, even taking that personal ordeal into account, there is something surprisingly arduous, even joyless at times, about Edwards’s second bid for the White House. Modern presidential campaigns tend to be aggressively upbeat and personality-driven; sure, every candidate has his favorite issues, but those issues generally exist mostly to color the candidate’s driving ambition with some shade of higher purpose. Edwards’s campaign feels oddly inverted. There’s no doubt he wants very badly to win, and yet there are times when the entire campaign seems little more than an excuse for him to talk about the issue with which he is now most closely identified: the case for the 37 million Americans living in poverty. The centerpiece of his campaign is a sprawling plan to eradicate poverty altogether by 2036. Echoing Robert Kennedy’s final campaign 40 years ago, Edwards, who has apologized for his Senate vote to authorize the invasion of Iraq, argues that Americans can’t prevail in a civil war abroad but that we can — and should — wage another war on poverty at home. Everything else in the campaign, Edwards seems to think, all these carefully orchestrated photo ops and drop-bys and van rides with the media, is the kind of empty political theater from which he declared himself liberated after his last presidential run. He gives the impression that he simply endures it.

In that last campaign, in 2004, Edwards, running as the unflappable optimist in the Democratic primaries, wrote an inspiring book about his days as a plaintiff’s lawyer; this time, his unusual entry into the now-standard field of campaign books is called “Ending Poverty in America: How to Restore the American Dream,” a collection of bleak and technical essays by leading liberal academics. In 2004, when Edwards repeated endlessly that he was the son of a millworker, he sounded proud and hopeful; now, when he brings up his humble beginnings, it’s mainly to suggest that he knows what it’s like to be one layoff or one X-ray away from destitution. This kind of grim “twilight in America” approach hasn’t been very successful for Democrats in recent decades. And yet Edwards could be poised to profit from the current moment in Democratic politics. Over the last few years, the party’s labor leaders and its left-leaning intelligentsia — Ivy League academics, columnists, economists — have become increasingly agitated about the ever-widening disparity between a tiny slice of wealthy Americans and the growing ranks of the working poor. These progressives see in Edwards’s campaign a test case for what they hope will be a more anticorporate, antitrade message for the Democratic Party.

The significance of what Edwards is saying, though, goes well beyond messaging and tactics. As the first candidate of the post-Bill Clinton, postindustrial era to lay out an ambitious antipoverty plan, he may force Democrats to contemplate difficult questions that they haven’t debated in decades — starting with what they’ve learned about poverty since Johnson and Kennedy’s time, and what, exactly, they’re willing to do about it.

If you’ve recently flipped to Lou Dobbs on CNN or opened the pages of a liberal political journal like The American Prospect, you might have the impression that America in the Bush years has slipped into a kind of Dickensian darkness, a period of unbridled greed and economic deprivation on a scale not seen in this country since the Great Depression. Like so many things in politics, this has some basis in truth, but only some. To compare Bush’s America with Herbert Hoover’s — or Lyndon Johnson’s, for that matter — is to engage in not very helpful hyperbole. According to the economists Thomas Piketty and Emmanuel Saez, the average income of an American taxpayer in 1929, using today’s dollars, was about $16,000 a year; the entire middle class, in other words, was poor by modern standards. It’s true that the official poverty rate, while fluctuating quite a bit, is pretty much unchanged from where it was 40 years ago (it was 14.2 percent in 1967, compared with just under 13 percent at last count), but it’s also true that what we call poverty has changed strikingly. When Johnson stepped onto that front porch in Inez, there were still rural poor who had no electricity, no running water, no primary-school education. Now most rural towns have access to satellite TV, and even the worst of the housing projects built in the 1960s — though thoroughly horrid places to live — come with solid roofs and indoor plumbing.

While poverty itself may little resemble what it was in 1929 or even in 1964, however, the distance between what poor and wealthy Americans earn has widened considerably in recent decades. Since the 1970s, the portion of national income attributed to the superrich — that is, the top one-tenth of 1 percent of earners — has essentially tripled. In fact, in recent years, the richest 1 percent of Americans have controlled the largest share of national income — currently 19 percent — since Franklin Roosevelt took the oath of office. If you’re in high demand as, say, a cosmetics C.E.O. or a basketball player, you’re making exponentially more than you would have made 30 years ago, while the lowest-earning Americans who buy your lipstick or watch your games on TV have barely seen their wages budge. It’s not that the poor are getting poorer, or that more Americans are falling below the poverty line, so much as it is that poor Americans are falling further and further behind those who succeed.

Economists have a lot of ideas about what factors are contributing to this worsening inequality, from Bush’s tax cuts to the ballooning pay packages of corporate executives, but the general consensus seems to blame a combination of technological advances and globalization. Automation means that companies can make the same products with fewer workers, and the emergence of a global work force means that they don’t have to make those products here anymore. As a result, wages for high-school graduates, who used to be able to get factory jobs, have stagnated, while highly educated workers have become increasingly valuable to companies seeking any intellectual advantage in an increasingly competitive world. Though inequality runs counter to what we think of as American values, there’s no consensus that it actually reduces growth — in fact, there are those who argue that inequality is a natural byproduct of growth. And yet, most social scientists seem to agree that, sooner or later, income inequality will exact a steep social cost, if not an economic one.

During the 1990s, Paul Romer, a Stanford economist, emerged as one of the world’s leading theorists on economic growth. Recently, though, Romer has changed his focus, and he told me that the country, too, is entering a new phase. For most of the 20th century, he explained, economists focused on stability — that is, understanding and controlling inflation and depressions. Then, toward the end of the century, growth became the central obsession. Now, Romer said, we are embarking on the next great challenge in American economics: mitigating inequality.