Editor's note: David Gergen is a senior political analyst for CNN and has been an adviser to four presidents. He is a professor of public service and director of the Center for Public Leadership at Harvard University's Kennedy School of Government. Follow him on Twitter. Michael Zuckerman is his research assistant.
(CNN) -- Space Shuttle Discovery started out as a way to discover what lies beyond us. Its last flight, taken earlier this week, helped to discover what now lies within us.
Piggybacked atop a specially outfitted 747, Discovery made its flyover Tuesday above Washington -- soaring over the White House and the Capitol, the Washington Monument and Arlington National Cemetery -- en route to Dulles Airport and its new (and final) home, the National Air and Space Museum's Udvar-Hazy Center.
All around Washington, people climbed up on rooftops, pulled off to the side of the road or gathered anywhere with a clear view to watch the shuttle's parting journey. The Washington Post reported tens of thousands on the Mall alone.
The tone of the onlookers -- reported on CNN.com and elsewhere -- varied, but two important emotions jumped out.
The first was nostalgia, even sadness. There was a sense that the retirement of the shuttle symbolized the trajectory of the country that sent her into space these past 30 years. CNN iReporter Danny Mills called the flyover "really bittersweet," while an online commenter wrote that, while watching: "Tears streamed down my face because this final flight represents the death of the space program. For me, it proves that America took a 'giant leap' to becoming a third-rate has-been."
That dejection is understandable. America, for the first time in three decades, does not have in place a program to send its astronauts into space. We pay the Russians for the service, with plans for a public-private partnership several years away to create new American spacecraft.
Space is not the only -- or most important -- frontier on which we're currently competing, but things are not going terrifically well on some of the others, either.
Our economy's stumbles and fitful starts in the past few years need no spelling out, and most projections have China's economy overtaking ours as the world's largest by 2030. The Economist recently projected that China's military spending could surpass ours by 2035.
Meanwhile, we are so failing to educate our children that a recent commission, co-chaired by former Secretary of State Condoleezza Rice and former New York City education chancellor Joel Klein, concluded that the poor state of K-12 imperils not just our economy but our national security.
But there was a second, more hopeful emotion in the reactions to the Discovery's final flight -- and that was pride. Pride at what the country had accomplished in the miracle of space flight; pride in what America can still do.
One woman told The Washington Post that the experience might propel her 9-year-old son to become an astronaut. Another wrote on CNN.com, "Now let's move on to bigger and better things so that our grandchildren can say the same about us in 50 years!" A third offered: "I hope we don't become a nation of nondreamers."
The spirit of the day called to mind a scene in "Mr. Smith Goes to Washington," when Jimmy Stewart first arrives in town and can't keep his eyes off the city's monuments and institutions. Like the onlookers pouring out of their offices or pulling off the road, he slips his handlers, pulled in by the draw of a sight-seeing bus headed for the Lincoln Memorial.
Perhaps part of Discovery's draw -- besides the sheer awe of a machine that had brought men and women to outer space and back -- was its timely reminder that there are still things we can do together as Americans.
The philosopher Michael Sandel has an important new essay in The Atlantic in which he argues that "we live in a time when almost anything can be bought and sold," in which we run the majority of our society like a marketplace. A corollary to this idea is that, as we privatize various projects, there are very few big things we do together as a nation anymore.
Sure, we still have to show up for jury duty and pay taxes, but increasingly our larger national efforts -- building infrastructure, transforming our schools, developing complex new technologies or conquering climate change -- drift along or are farmed out to private interests. Our wars are fought by an elite but all-volunteer military ("the forgotten one percent"), supplemented by defense contractors and other private companies.
If Discovery's last ride rekindled our pride in what we can accomplish together as citizens in a vibrant country, it should also rekindle our call for leaders who can reunite us in tackling those big challenges.
At our Center for Public Leadership at the Harvard Kennedy School, we conduct a yearly poll, "The National Leadership Index," to take the pulse on America's judgment of its leaders.
This past year's brought us a near record-low. Only 21% of those surveyed believe that our country's leaders are effective and do a good job, while 77% believe we have a leadership crisis in the country today and that, unless we get better leaders, we will decline as a nation. As Harvard Business School professor Nancy Koehn puts it: "At this critical inflection point for the country ... people are parched for leaders who can lay out a credible mission."
A half-century ago this year, a young president visited Rice University in Texas to deliver a major address on his plan to put a man on the moon before the end of the decade. President John F. Kennedy said this:
"We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard; because that goal will serve to organize and measure the best of our energies and skills; because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win."
As the reactions from folks watching the shuttle's last voyage on Tuesday attest, that spirit of discovery still lies within us here in America. But the search goes on for leaders who will ensure it doesn't perish from the Earth.
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The opinions expressed in this commentary are solely those of David Gergen and Michael Zuckerman.