Lee Hamilton remembers that when he came to Washington 45 years ago as a freshman Democrat from Indiana, he made a dumb parliamentary error that would have scuttled the bill he was advocating. The House Republican leader at the time, Gerald Ford, sent over one of his colleagues to help Hamilton fix the mistake.

The story sounds almost unbelievable in today's bitterly partisan climate, and Hamilton smiles and shakes his head as he tells it. Was there really a time like that, when party interests were subordinate to making the country work? And how could the America of 2010, a nation with an increasingly dysfunctional political system, ever get back to that Arcadia?

I asked Hamilton to ruminate about these questions recently, for two reasons: First, because at 79, he's one of the wisest and most experienced people in Washington, and second, because he will be packing his bags in November and returning home to run an institute at Indiana University. People like him, who know what it was like for government to operate effectively, are a dwindling resource in the capital.

"The big question in politics today is, 'What happened to the center?' " he says. That erosion was evident in Tuesday's primary elections, in which dissident Republicans backed by the Tea Party movement toppled establishment Republicans in Delaware and New York. It was another sign that, as Hamilton says, "The centrifugal forces have become dominant."

Hamilton offered a simple formula for maintaining sanity in this period of insane politics: Put the interests of your country first. "You must encourage the mind-set that if you're elected, your first obligation is to see that America works and succeeds," he said. Political loyalties must come second.

That may sound naive -- like telling someone who's depressed to cheer up. But it conveys a larger point: If a politician's goal is to enhance the country's success, then he must retain the flexibility to make the pragmatic compromises that can solve problems. "If you get a politician locked into a position, it reduces his freedom of maneuver," warns Hamilton, and it becomes impossible to achieve consensus.

Hamilton has fought to defend the ground for compromise and consensus during this divisive decade, as vice chairman of the bipartisan Sept. 11 commission and co-chairman of the Iraq Study Group. He has also served as president of the Woodrow Wilson Center since he retired from Congress in 1999.

Hamilton still manages to look like someone from the middle of America, even after all these years inside the satanic Beltway. He leans back in his chair and stretches his gangly legs out as if he's sitting on a porch back home. And then there's that trademark crew cut, which bespeaks an America when haircuts were cheaper and blow dryers weren't a politician's best friend.

The Indiana Democrat remains unflappable, even at a moment when American politics seems to be suffering a collective nervous breakdown. The problem with politics today, says Hamilton, isn't just that it's partisan -- the reigning ideologues when he arrived in Washington, Hubert Humphrey and Barry Goldwater, were partisan, too -- but that it has become "mean-spirited" and bitter.

The decline of governance has coincided with the rise of interest groups. Hamilton takes the example of agriculture policy: When he came to Congress, there were three big lobbying groups -- the Farm Bureau, the Grange and the National Farmers Union. Today, it seems every commodity has its own aggressive advocacy group. And business groups, while denouncing government in general, all want their own particular breaks.

Hamilton has been a supporter of President Obama. But he offered some constructive criticism, too. Looking back on the health-care debate, Hamilton said, it's clear that there wasn't yet consensus on a reform package -- and "you don't have a solution to a problem in this country unless you have a consensus." He faults Obama, too, for not yet finding a pastorly voice that could unite Americans in crisis. "Obama is still reaching for that," he said.

I asked Hamilton if he thought that America, with its political problems, is a country in decline. He quoted Lincoln's famous Civil War speech asking whether a divided nation "can long endure."

"That was the question at Gettysburg, and it's the operative question today," he said. "It's not written in the stars that we'll always be No. 1 and we'll always prevail." But regardless of whether America is up or down, Hamilton said, "our responsibility is the same, which is to make the country work."

davidignatius@washpost.com