It is the very essence of the American Dream: an irrepressible confidence that our children will live better than we do.

And now it is gone.

It has been slipping for some time, really, but a Wall Street Journal/NBC News poll this month put an exclamation point on Americans’ lost optimism.

When asked if “life for our children’s generation will be better than it has been for us,” fully 76 percent said they do not have such confidence. Only 21 percent did. That was the worst ever recorded in the poll; in 2001, 49 percent were confident and 43 percent not.

When you look closer, things seem even worse, if that’s possible. I called Fred Yang, the Democratic pollster who conducted the survey along with Republican Bill McInturff, and he told me the pessimism was universal. The wealthy were as down as the poor (75 percent and 73 percent, respectively) and even those who felt that they were doing well personally didn’t think their children would do as well (61 percent). Women are as grim as men, and there’s little difference according to race (whites are slightly more pessimistic and Hispanics slightly less) or by region (Westerners are slightly less gloomy than the others).

The young are relatively less pessimistic than the old (64 percent to 86 percent) but still plenty discouraged in absolute terms. Republicans (88 percent) were more dour than Democrats (61 percent), just as Democrats were more dour than Republicans when the question was asked in 2006 (56 percent to 71 percent) during a similar stage in George W. Bush’s presidency.

In other words, the gloom goes beyond wealth, gender, race, region, age and ideology. This fractious nation is united by one thing: lost faith in the United States.

Certainly, some of the dark outlook has to do with the slow recovery. And there’s justification for the pessimism: Millennials are, by some measures, the first generation in U.S. history to see a decline in living standards. But now the economy is improving measurably, and optimism hasn’t followed. “I keep thinking, boy, these numbers are going to turn around, and they don’t turn around, they’re enduring,” said Andrew Kohut, founding director of the Pew Research Center.

Kohut attributes the phenomenon to structural problems such as income inequality, and he notes that people in other advanced countries have also been more pessimistic since the 2008 economic collapse. That’s true, but Americans were already plenty pessimistic about the next generation (65 percent to 27 percent) back in 2006, when the economy was strong.

Yang’s suspicion, which I share, is that something deeper is also at work: Americans are reacting, in part, to the breakdown of the political system, which leaves people quite rationally worried about American decline and the nation’s diminishing ability to weather crises. “One of the hallmarks of being an American is the optimism that your children will be better off,” Yang told me. The lost optimism, he said, “says a lot about how shaken we are by the inability of our political system to address seemingly easy issues, and it leaves us worried about the future.”

In a narrow sense, this is good news for President Obama because it means the problem is not of his making but the result of two decades of scorched-earth politics. That’s bad news for the rest of us, though, because the problem is larger than any leader’s ability to bring hope and change.

For much of U.S. history, optimism was a given. The Post’s polling analyst, Scott Clement, came up with a 1942 survey by Princeton University’s Office of Public Opinion Research that found U.S. parents, by 43 percent to 27 percent, expected their children to be better off in 20 years. A Roper poll in 1983 found that 54 percent thought it likely that children would have a better life than their parents, versus 44 percent who didn’t. In 1990, the WSJ/NBC poll found the optimists besting the pessimists, 50 percent to 45 percent.

Since then, various polling outfits have had different results, with some finding generally higher levels of optimism and others closer to the NBC/WSJ results. But virtually all polling shows a steep decline in optimism since the late 1990s and early 2000s.

Yang doesn’t see that improving much, even as the economy does. “The unsettledness of the public is what is normal now,” he said. “To me, this is less about economic reality than about our political system — our lack of confidence that our political leaders, regardless of party, are equipped to deal with the future.”

Twitter: @Milbank

Read more from Dana Milbank’s archive, follow him on Twitter or subscribe to his updates on Facebook.