But first, a quick caveat. Age and political context are not the only factors that decide an individual's political orientation. Just ask my libertarian friends. Party identification, with all of its associated reinforcement effects, matters tremendously. So too does race, gender, class, personal experiences, the friends you chose, the partner you married, the state you come from, and all the other ineffable characteristics that figure into an individual's development. This campaign has suffered from no dearth of conversation about most of those pressures. John Edwards' wealth, Hillary Rodham Clinton's gender, Obama's race and everyone's spouses have been broadly discussed, and that's as it should be. But generational effects shouldn't be ignored either.

McCain came of age as the exultation of our seemingly clean triumph over the Axis countries shaded into the haunting anxiety of the Nuclear Age and superpower competition. When he says, as he often does, that "the transcendent challenge of the 21st century is radical Islamic extremists," it needs to be understood in that context: The Axis had a real shot at world domination. The Soviet Union's nuclear arsenal could have annihilated America. McCain, like others of his generation, is a man accustomed to transcendental challenges that come from states, the only actors traditionally able to pose a serious threat.

Thus, he has a tendency to play up the role of states in terrorism. In February 2003, McCain told the Center for Strategic and International Studies that "the links between Iraq and Al Qaeda are hotly debated today. Terrorist trails are designed to be obscure. Saddam [Hussein] knows that." In McCain's hands, the very absence of meaningful linkage between Hussein and Osama bin Laden became evidence of their collaboration. Similarly, McCain has often been criticized for repeatedly, and mistakenly, claiming that Iran is accepting and training members of Al Qaeda. But it is a revealing error. In both cases, McCain grasped to connect the threat of a diffuse terrorist network to traditional states. Searching for the transcendent danger, he overlooked the atomized threat.

By contrast, Obama passed the tumultuous '60s watching cartoons. He was 14 when the Vietnam War ended. By the time he had graduated from law school, at 29, the Soviet Union had crumbled. Which explains his apparent confusion at being drafted into the culture wars of the '60s.

Obama has suffered in the campaign, for instance, for his association with former Weatherman Bill Ayers, who's now an aging intellectual and activist in Chicago. Pressed on the connection in April's ABC debate, Obama replied: "The notion that somehow, as a consequence of me knowing somebody who engaged in detestable acts 40 years ago when I was 8 years old, somehow reflects on me and my values doesn't make much sense."

To Obama, those battles really don't make sense, and the hunch that they're fading into the past was part of the original rationale for his candidacy. In his book, "The Audacity of Hope," Obama wrote: "In the back and forth between [President] Clinton and [then-House Speaker Newt] Gingrich, and in the elections of 2000 and 2004, I sometimes felt as if I were watching the psychodrama of the baby boom generation -- a tale rooted in old grudges and revenge plots hatched on a handful of college campuses long ago -- played out on the national stage."

Those are just two examples of many. The ages of the candidates have a profound effect on the direction of the campaign, but because of philosophy and policies, not lipid profiles and treadmill tests. The question, of course, is which candidate's America will more closely approximate that of a majority of voters. Because in the end, although the age of the candidates may matter, it won't decide the election. Rather, the age of the electorate will.