On April 27 1968 the vice president, Hubert Humphrey, announced his presidential candidacy. It was a particularly troubled moment in America's recent history. Just three weeks after Martin Luther King's assassination, the cities were still scarred by riots while the country as a whole was deeply divided over the Vietnam war.
Presumably seeking to capture the mood of the nation, Humphrey started his speech thus: "Here we are, the way politics ought to be in America, the politics of happiness, the politics of purpose, the politics of joy; and that's the way it's going to be, all the way, too, from here on out." Within six weeks Bobby Kennedy had been assassinated.
America's self-image as the home of unrelenting progress - a nation of historic purpose and unrivalled opportunity where tomorrow will always be better than today - is the linchpin of its political and popular culture. Optimism, it seems, is a truly renewable national resource. It was used to build Bill Clinton's "bridge to the 21st century" in 1992, and powered the alarm clocks for Reagan's "new morning in America".
"The American, by nature, is optimistic," said John F Kennedy. "He is experimental, an inventor and a builder who builds best when called upon to build greatly." This optimism is the source for much of what makes the US simultaneously so revered and reviled, dynamic and deluded, around the world.
On one hand it articulates a hope, bordering on certainty, that a better world is not just feasible but already in the making. Released from the hogties of tradition and formality, such confidence is driven by possibility rather than the past. Winston Churchill once said he "preferred the past to the present and the present to the future". An American politician who wanted to get elected would say precisely the opposite. This optimism underpins the notions of class fluidity and personal reinvention at the core of the American dream. Where others might ask "Why?", it asks "Why not?". Such is the root of so much that is great about America's economy, culture and politics.
On the other hand this optimism has within it the notion that the US is the exclusive repository of these hopes and the sole means by which a better world can be made. Unfettered by history, consensus or empirical evidence, it is driven by myth rather than material circumstances. Even as class rigidity entrenches and personal reinvention slips, the dream remains. Like Stephen Colbert's spoof of George Bush, it has the capacity to "believe the same thing Wednesday that [it] believed on Monday, no matter what happened Tuesday". It posits America as the world's future whether the world wants it or not. Such is the root of so much that is terrible about America's economy, politics and foreign policy.
This sense of optimism has been in retreat in almost every sense over the past few years. According to Rasmussen polls, just 21% of Americans believe the country is on the right track, a figure that has fallen by more than a half since the presidential election of 2004. Meanwhile only a third think the country's best days are yet to come, as opposed to 43% who believe they have come and gone - again a steep decline on three years ago. These are not one-offs. In the past 18 months almost every poll that has asked Americans about their country's direction has produced among the most pessimistic responses on record - a more extended period than anyone can remember since Watergate.
America, in short, is in a deep funk. Far from feeling hopeful, it appears fearful of the outside world and despondent about its own future. Not only do most believe tomorrow will be worse than today, they also feel that there is little that can be done about it.
There are three main reasons. Closest to home is the economy. Wages are stagnant, house prices in most areas have stalled or are falling, the dollar is plunging, and the deficit is rising. A Pew survey last week showed that 72% believe the economy is either "only fair" or poor and 76% believe it will be the same or worse a year from now. Globalisation is a major worry. Of 46 countries polled recently, the US had the least positive view on foreign trade and one of the least positive on foreign companies.
The sense that things will improve for the next generation has all but evaporated. Another Pew poll from last year found that only 34% of Americans expected today's children to be better off than people are now - down from 55% shortly before President Bush came to power.
Second is the Iraq war and the steep decline in America's international standing it has prompted. A global-attitudes Pew poll from last year showed that 65% of Americans believe the country is less respected by the rest of the world than it was - double the figure of 20 years ago. The fact that only half those polled thought this was a problem is telling.
For if the war in Iraq were going well then this probably wouldn't matter. But it isn't. All surveys show that for some time a steady majority of the public believe the war was a mistake, is going badly and that the troops should be withdrawn. One of the central factors in which America's self-confidence was predicated - global hegemony based on unrivalled military supremacy - has been fundamentally undermined.
Last week Lieutenant General Ricardo Sanchez, the former top commander of US troops in Iraq, spelled out the national despair, branding the war a "nightmare with no end in sight".
Which brings us, finally, to the political class. Once again the American public have lost faith. The rot starts at the top. Almost as soon as they elected Bush in 2004 they seemed to regret it. Since Katrina, his favourability ratings have been stuck in the 30s and show no signs of moving - or at least not upwards. Bush's only comfort is that public approval of the Democratically controlled Congress is even worse, hovering just below where it was shortly before the 2006 elections. In other words, however Americans believe their country will return to the right track, they no longer trust politicians to get them there.
Little suggests that anything will change any time soon. After four years of being told they were winning a war they have been losing and are better off when they are not, Americans are more wary of political happy talk than they have been for a long time. But that doesn't mean they want to hear sad talk instead, even if it happens to be true. For the central problem is not that they were lied to - though that of course is a problem - but that they have constantly found some of these lies more palatable than the truth. Bush may have exploited the more problematic aspects of this optimism. But he did not create them. Enough of the American public had to be prepared to meet him halfway to make his agenda possible.
Herein lies the challenge for the presidential candidates in the coming year - how to respond to this pessimistic mood without reflecting or discussing its root causes: to lay out a plausible explanation of how Americans can get their groove back, without examining how they got in this rut in the first place.
Gary Younge, the Alfred Knobler Journalism Fellow at The Nation Institute, is the New York correspondent for the Guardian and the author of No Place Like Home: A Black Briton's Journey Through the Deep South (Mississippi) and Stranger in a Strange Land: Travels in the Disunited States (New Press).
© 2007 The Guardian