Minnesotans have always relished feisty political debates. (Long winters favor indoor sports.) But the national rancor this summer over health care and more has been troubling even to the those of us in the public debate business. We've wondered: Is America's partisan divide growing so wide that it is damaging the national interest, and maybe even imperiling democracy?

Our worry evidently isn't just a case of overwrought Minnesota Nice sensibility. One of the nation's most respected political thinkers, David Gergen, confessed last Thursday in Minneapolis that he's fretting about the same thing.

The CNN commentator, director of the Center for Public Leadership at the Harvard Kennedy School, and adviser to four presidents -- three Republicans and one Democrat -- shared his concern as part of the Summit on Leading in Crisis, a panel discussion hosted by the George Family Foundation and moderated by former Medtronic CEO Bill George at the University of Minnesota.

Today's American leaders confront two kinds of crises, Gergen observed -- prolonged economic trouble and the trouble that analysts see coming a decade or so from now if present trends continue in Social Security and Medicare costs, health care spending, educational achievement, energy consumption, environmental degradation and more.

Those crises pose more difficult challenges for the nation than the kind that arise suddenly from an external source, Gergen said. A disaster such as a 9/11 attack brings Americans together, and prior emergency planning can cushion that kind of blow, he noted.

A crisis looming on the horizon is the most difficult for American leaders to manage well, he said. A sense of denial, Americans' native optimism and politicians' willingness to pander for votes make it too easy to "kick the can down the road" -- even though delay likely will make the situation worse.

Americans' response this summer has been to turn on each other. "We're at each other's throats," Gergen said. He spoke bluntly about two chilling possible consequences of the "rancid" debate: violence directed at elected leaders, and erosion of the country's ability to govern itself.

"This is not theoretical. This is something that's quite real," he said. "We are facing a deteriorating situation" in the ability of Americans to constructively work together to solve major problems. If those problems go unsolved, they threaten the ability of the United States to remain a leading world power long into the 21st century. "This is a test of the greatness of this country," he said.

Meeting and passing the test will require larger doses of self-restraint and collective maturity than Americans lately have been exhibiting. As noted another Thursday panelist, Anne Mulcahy, chair of Xerox Corp., the nation's corporate and academic leaders can and should provide examples of constructive leadership. Gergen correctly noted that the nation's media ought to question their role in amplifying foolish conversations that do little to equip citizens to better solve shared problems. Politicians bear particular responsibility for curbing excessive vitriol in public debate. But they do not bear that responsibility alone.