This space long has argued that national security defines the federal government's principal obligation. The president performs many roles. None surpasses that of commander-in-chief in importance. Issues relating to defense and foreign policy belong at the top of party platforms. As it opened, the 2008 campaign offered the potential for a compelling debate on America's place in the world. John McCain and Barack Obama ably articulate competing visions. Yet the economic crisis ensured that a sustained exchange would not occur. The first debate, for instance, was supposed to focus on national security. The economy led the agenda and proved of greater interest to viewers. Although foreign policy retains its heft, it seems safe to say the election will not hinge on the candidates' positions on NATO. Potential secretaries of the treasury have vaulted over potential secretaries of defense and potential secretaries of state in the public imagination.

We understand.

Challenges relating to the defense of the homeland and to America's standing abroad will not disappear, however. The economic crisis itself is of global scope; its causes include global factors; its consequences will have implications for U.S. foreign policy. At this moment the only so-called superpower does not boast a super economy. America's era of worldwide economic dominance began to wane some time ago. The crisis closes another chapter of American triumphalism. Well might a country blessed and blessing relearn humility's virtues and joys.

References to generational influences and identities typically strike us as contrived, self-serving, and boring. McCain and Obama come from different generations, and for once the distinction might prove defining. McCain was forged by national and personal struggle. His is a world of ideals but without illusions. He understands power's purposes and its limits. A McCain presidency would assert American interests but, we believe, without the unilateralism that has undermined U.S. policy recently. It is impossible to conceive of a President McCain snapping, "Bring 'em on," during the heartbreaking havoc of war. Obama belongs to a generation at once freshingly cosmopolitan -- at ease with a world beyond geography's confining seas and beyond isolationism, ignorance, withdrawal, and other aspects of the American temptation -- and oblivious to history made by others. Fouad Ajami, professor of Middle Eastern Studies at Johns Hopkins, writes:

"The Obama way is glib: It glides over the world without really taking it in. It has to it that fluency with political and economic matters that can be acquired in a hurry, an impatience with great moral and political complications. The lightning overseas trip, the quick briefing, and above all a breezy knowingness. Obama's way is the way of his peers among the liberal, professional elite."

And that explains much of Obama's attraction. People project. This does not mean that on specific questions Obama is automatically wrong or that as president he would betray his countrymen. American foreign policy reflects a remarkable consistency -- and resilience -- not only during times such as the Cold War but throughout national history. There have been twists and turns to be sure, but few radical breaks. Republicans and Democrats alike have recorded successes and failures. Reality tends to trump sentiment and ideology. Those who hope Obama fundamentally will alter U.S. foreign policy court disappointment. Although those who believe his approach is fundamentally flawed likely would be relieved by his practice, most would not want to take the risk. Obama's advisers inlcude Richard Holbrooke and Dennis Ross, neither of whom qualifies as a hot head. Certain Obama statements also suggest he would restore America's global reputation with a pre-emptive grovel. McCain is the Harry Truman in this race.

. . .

Items on the slate include Iraq (McCain was right when George Bush was wrong), Iran, the Middle East generally, North Korea, Russia, NATO expansion, the former Soviet "republics" and satellites, China, Hugo Chavez (otherwise known as Fidel), Latin America, trade, climate change (yes, it is happening, and humans contribute to the process), energy, Darfur, international development, natural calamities (earthquakes, tsunamis), terrorism, AIDS, and events and personalities as yet unforeseen.

Questions relating to defense include force structure -- and the projection of force. What forms will the wars of the future assume? Our advice to both candidates: Read Philip Bobbitt's Terror and Consent: The Wars for the 21st Century. The difficulties encountered in Iraq reflect, in part, mistaken military assumptions. (Diplomatic blunders contributed, too. For several years incompetence was a common vice.) We have confidence in the personal abilities of McCain and Obama. We cannot deny troubling questions regarding McCain's temperament. Obama's worldview generates considerable doubt. The experience contest is not close.

On national security, McCain prevails.

Regardless of the outcome next month, the U.S. should welcome vigorous debate during the years ahead, as long as partisanship stops at the shores. And we deign to call ourselves "realists."