Ten years ago next month, when the Dow was at 6437.10 and the Nasdaq was at 1300.12 -- on Wednesday they were 12,176.54 and 2384.94, respectively -- Alan Greenspan warned against "irrational exuberance." But Tuesday's election results were fresh evidence that two events that profoundly shaped American politics during the past two presidencies were episodes of irrational exuberance unrelated to economic behavior.

The Democratic episode was the Clintons' attempt to radically restructure and semi-socialize the 16 percent of the economy that is the health-care sector. The Republican episode was -- is -- Iraq.

The Clintons' health plan never even came to a vote in a Congress their party controlled. Two years later President Bill Clinton was silly to say that "the era of big government is over," but a different era was over. It was the era of confidently comprehensive, continent-wide attempts to reform complex social systems.

Ten weeks before the 1994 elections, Martha Derthick of the University of Virginia wrote, on this page, of the plan produced by Hillary Clinton's 500-person task force: "In many years of studying American social policy, I have never read an official document that seemed so suffused with coercion and political naivete ... with its drastic prescriptions for controlling the conduct of state governments, employers, drug manufacturers, doctors, hospitals and you and me."

The Clintons' health-care plan validated the perception that their party was gripped by both intellectual hubris and intellectual sloth -- meaning, it was still in a New Deal and Great Society frame of mind. This perception contributed to the 1994 elections, in which Republicans gained 52 House seats (and soon five more from party-switchers) -- ending 40 years of Democratic control of the House -- and eight Senate seats (plus two party-switchers).

Now 12 years of Republican control of the House are ended because of the Bush administration's foreign policy equivalent of the Clinton administration's overreaching regarding health care. Republicans should feel relieved: Considering that in November 1942, 11 months after war was thrust upon America, President Franklin Roosevelt's party lost 45 House and nine Senate seats (there were then just 96 senators), Tuesday's losses were not excessive punishment for the party that has presided over what is arguably the worst foreign policy disaster in U.S. history.

Subsequent elections will reveal whether this election is a harbinger of a new and chronic Republican weakness. For nearly two generations -- since the Democratic Party fractured over Vietnam in 1968 and nominated George McGovern in 1972 -- the Republican Party has benefited from a presumption of superior realism regarding the essential presidential competence, national security. Time -- actually, 2008 -- will tell if Iraq will do the kind of lingering damage to the Republican Party that was done by the Depression, which made the party suspect for a generation regarding the conduct of domestic policy.

The departure of Donald Rumsfeld, a remarkably swift ratification of the electorate's roar Tuesday, removes an impediment to the possibility of a modus vivendi between the president and the congressional majority. Rumsfeld's replacement, Robert Gates, by virtue of his service on the Iraq Study Group chaired by James Baker and Lee Hamilton, is already immersed in the agonizing choices that must be made. And having been deputy national security adviser in 1991, Gates knows why the first President Bush declined to extend Operation Desert Storm beyond the liberation of Kuwait to regime change in Baghdad. Shortly after the war, the secretary of defense then, Dick Cheney, said why arguments for "going to Baghdad" had been "fallacious."

"Once you've got Baghdad, it's not clear what you do with it," he told the New York Times. "It's not clear what kind of government you would put in place of the one that's currently there now. Is it going to be a Shia regime, a Sunni regime or a Kurdish regime? Or one that tilts toward the Baathists, or one that tilts toward the Islamic fundamentalists? How much credibility is that government going to have if it's set up by the United States military when it's there? How long does the United States military have to stay to protect the people that sign on for that government, and what happens to it once we leave?"

Good questions, the answers to which we now know.

Gates, who was there when the questions were asked, seems to be of the realist school, reluctant to engage in regime change as a prelude to nation-building. And we may hope that as director of the CIA he learned the most important thing a government can know -- what it is that it doesn't know. Such knowledge inoculates governments against irrational exuberance.

~George Will is a Washington Post columnist. E-mail: georgewill@washpost.com.