Here’s what we believe: For most of our history, Americans — who planted colonies on inhospitable shores, rebelled against the most formidable power on Earth, settled a wild continent, built an industrial empire, broke the gravitational pull of the planet and landed on the moon — have been a wildly optimistic people. Only in this new century have we come to believe the next generation’s fate might be worse than ours.

Here’s what’s true: We’re not that optimistic, and haven’t been for years, even decades. For decades we’ve believed that those who follow us will have it harder than we had it.

This is the great American disconnect. We’re living a myth, but then again, it is the myth that defines us — and our politics.

Today, by a 2-to-1 margin, Americans believe the next generation will be worse off than we are. Some 23 years ago, Americans believed by a 2-to-1 margin that the next generation would be worse off than we were. Remember that the 1989 poll was taken only five months after the greatest optimist in presidential history, Ronald Reagan, had left office and when his handpicked heir, George H.W. Bush, was still enjoying a political honeymoon.

As that legendary political commentator Richard Farina might say: Been down so long it looks like up from here.

In fact, in three decades of CBS News/New York Times polling, Americans have consistently held the pessimistic view. The only exception came during the last months of the presidency of Bill Clinton, which goes a long way toward explaining why the Democrats countered the “Are you better off?” taunts of the Republicans by putting the 42nd president on stage at their convention for what they knew would be a bravura performance.

The truth is that life is tough and always has been, even in the richest country on Earth, even in a land endowed with great resources, even in a nation peopled with workers strong in mind as well as body and empowered with grit, dedication and intelligence. History may be the story of humankind’s great achievements — the electric light, air travel, the microwave oven, the iPad — but it is just as much the story of humankind’s great disappointments.

When World War I, a needless conflict produced by heedless European leaders, ended, the Great Depression followed, the League of Nations fizzled and a depression fell across the globe. World War II, the worst calamity in all of history, ended with freedom triumphant, but within months the world settled into a debilitating Cold War that drained our resources and spirit and warped our foreign and domestic policies.

Then Communism fell, but soon the peace dividend disappeared, terrorism touched our shores, our freedoms were threatened by our enemies and by our own government, and then an incapacitating recession sapped our energies and dampened our hopes.

Yes, that’s a short, oversimplified and relentlessly pessimistic history of the last century. But the beginning of knowledge is the recognition of our true selves, and in fact Americans are both optimistic and pessimistic, bravely approaching the future — but deeply afraid of its uncertainty.

It was rational to fear the effects of the Great Depression and to worry about the outcome of World War II. Today we know that both the economic and the geopolitical threats were defeated, but those things were not known in 1930 and 1942, respectively, and there was ample reason to believe that deprivation and Nazism might prevail. Today we say we won those battles because of the irresistible power of freedom (in the marketplace, in the voting booth and in the mind), but those triumphs weren’t inevitable. It was good, very good, that they happened, but it was never a sure thing.

All of which is why the conversation about whether we feel the next generation will have it better or worse is really beside the point, though maybe irresistible.

There is so much we don’t know: Will Iran get the bomb? Will the economy return to robust health? Will the enemies we don’t know be even worse than the ones we do know, and will one challenge be replaced by another, just as Nazism and Fascism were followed by Communism — and just as the threat from the Soviets was replaced by the threat from al-Qaida?

And given so much uncertainty, it is natural — rational, even — to feel unsettled. Things are bad now, to be sure. Even Democrats acknowledge the Obama administration hasn’t been able to make things right, to return us to the world we knew and the world we now think seems so sunny, forgetting of course the clouds of yesterday.

The question isn’t our expectations for the next generation. The question is whether the current generation has the will to assure that the next generation has a fair chance to prevail over the threats it encounters.

The question isn’t whether the next generation will live more comfortably, but whether the current generation has the imagination to find solutions to the entitlements crisis, the energy challenge, the cost of health care and the threat of weapons of mass destruction.

The presidential candidates are in a pointless debate. Of course we feel the next generation will have it worse than we did, a sentiment fortified by this month’s report that U.S. median income is the lowest since 1995. But we’ve been feeling that way for years — and it shouldn’t alarm us, whether we’re Democrats struggling to defend the president or Republicans trying to use our unease to topple the president.

The key to U.S. history isn’t that we thought the future would be brighter, but that we did things to assure it would be. Use that as the prism through which you view the campaign, and your perspective will be markedly different.

Candidates love to say American elections are about the future. But our own history and our own polling data show us that they are not about what life may be in the future but whether we have the capacity to control the present — and thus to mold the future. That’s what Campaign 2012 is really about, or should be.