LOSING HURTS MORE than winning feels good. This simple maxim applies with equal power to virtually all areas of human interaction: sports, finance, love. And war.

Defeat in war damages societies quite out of proportion to what a rational calculation of cost would predict. The United States absorbed the loss in Vietnam quite easily on paper, for example, but the societal effects of defeat linger to this day. The Afghanistan debacle was an underrated contributor to Soviet malaise in the 1980s and a factor in perestroika, glasnost and eventually the dissolution of the Soviet Union. Defeats can have unintended, seemingly inexplicable consequences.

And as any sports fan can tell you, the only thing that feels worse than a loss is an upset. An upset demands explanation and requires that responsible parties be punished.

The endgame in Iraq is now clear, in outline if not detail, and it appears that the heavily favored United States will be upset. Once support for a war is lost, it is gone for good; there is no example of a modern democracy having changed its mind once it turned against a war. So we ought to start coming to grips with the meaning of losing in Iraq.

The consequences for the national psyche are likely to be profound, throwing American politics into a downward spiral of bitter recriminations the likes of which it has not seen in a generation. It will be a wedge that politicians will exploit for their benefit, proving yet again that politics is the eternal enemy of strategy. The Vietnam syndrome divided this country for decades; the Iraq syndrome will be no different.

The battle for interpretation has already begun, with fingers of blame pointed in all directions in hastily written memoirs. The war’s supporters have staked out their position quite clearly: Attacking Iraq was strategically sound but operationally flawed. Key decisions on troop levels, de-Baathification, the disbanding of the Iraqi army and the like doomed what otherwise would have been a glorious war.

The American people seem to understand, however — and historians will certainly agree — that the war itself was a catastrophic mistake. It was a faulty grand strategy, not poor implementation. The Bush administration was operating under an international political illusion, one that is further discredited with every car bombing of a crowded Baghdad marketplace and every Iraqi doctor who packs up his family and flees his country.

The only significant question still hanging is whether Iraq will turn out to have been the biggest strategic mistake in U.S. history. Vietnam was a much greater moral disaster, of course, and led to far more death and destruction. But, just as the war’s critics predicted in the 1960s, Vietnam turned out to be strategically irrelevant. Saigon fell, but no dominoes followed; the balance of Cold War power did not change.

Iraq has the potential to be far worse. One of the oft-expressed worst-case scenarios for Iraq — a repeat of Lebanon in the 1980s — may no longer be within reach. Lebanon’s simmering civil war eventually burned itself out and left a coherent, albeit weak, state in its ashes. Iraq could soon more closely resemble Somalia in the 1990s, an utterly collapsed, uncontrollable, lawless, failed state that destabilizes the most vital region in the world.

Hopefully at some point during the recriminations to come, the American people will seize the opportunity to ask themselves a series of fundamental questions about the role and purpose of U.S. power in the world. How much influence can the United States have in the Middle East? Is its oil worth American blood and treasure? Are we really safer now that Iraq burns? Might we not be better off just leaving the region alone?

Perhaps at some point we will come to recognize that the United States can afford to be much more restrained in its foreign policy adventures. Were our founding fathers here, they would surely look on Iraq with horror and judge that the nation they created had fundamentally lost its way. If the war in Iraq leads the United States to return to its traditional, restrained grand strategy, then perhaps the whole experience will not have been in vain.

Either way, the Iraq syndrome is coming. We need to be prepared for the divisiveness, vitriol, self-doubt and recrimination that will be its symptoms. They will be the defining legacy of the Bush administration and neoconservatism’s parting gift to America.