"When it comes to foreign policy, experience is a highly overrated asset." So says a former British foreign service officer named Jonathan Clarke, who has created a blog called Swoop ( http://theswoop.net) dedicated to undermining Washington's fondness for conventional wisdom.

What my friend Clarke means is that the set of issues and strategies that shaped the Cold War generation has passed. He's a product of that generation, having served at the sharp end of the spear for the British government in various Cold War hot spots. But that era is over. The intellectual matrix formed by the Soviet threat, and before that by Hitler's rise in Germany, needs to be reworked. There is a new set of problems and personalities -- and if America keeps trotting out the same cast of characters and policy papers, we will fail to make sense of where the world is moving.

The experience issue will dominate the final weeks of the Democratic primary campaign. Hillary Clinton's only remaining trump card is that she has been in the White House before and will be ready, as she repeats so tirelessly, from Day One. But ready for what? For a recapitulation of the people and policies that guided the country in the past? That's an attractive proposition only if you think that the world of the 1990s -- or '80s, or '70s -- can be re-created.

The experience gap will overshadow even more the general election race against John McCain, the presumptive Republican nominee. With his every sinew, McCain embodies the idea of a wise, battle-tested man. "I'm not the youngest candidate, but I am the most experienced," he said after winning the Wisconsin primary Tuesday night. It's clear he hopes this pitch will carry him all the way to the White House. He's the tough old fighter pilot; he has fought the Cold War battles; he knows how to protect the nation in a time of danger. That's the McCain strategy in one compound sentence.

The assumption that experience equates with good judgment is a hard one to shake. We tend naturally to defer to the person who has been there before, measured the adversary, learned how the game is played. Yet if ever there were a test of the efficacy of experience, it was the Bush administration's decision to go to war in Iraq and its subsequent management of the postwar occupation. Bush's national security advisers were arguably the most experienced in modern times. But their performance was often very poor. That was partly, I think, because they overlaid the post-Sept. 11 challenges on a Cold War template about the uses of military power.

We are the last major nation to make the transition from Cold War thinking to something new. China and India are rising thanks to new leadership elites that understand how to succeed in global markets; Russia is about to elect a new president whose formative experiences came after the fall of the Soviet Union; Pakistan has just rebuffed its own durable Cold Warrior, Pervez Musharraf; even Fidel Castro, perhaps the iconic survivor of the Cold War, has decided to step down. Only in America could John McCain seriously campaign for leadership as a symbol of the past.

The utility of inexperience was explained to me last week by Dmitry Peskov, the spokesman for President Vladimir Putin. He said that what's attractive for Russians about Dmitry Medvedev, who is certain to be elected as Putin's successor next Sunday, is that he embodies "a generation that was not shaped by the Soviet Cold War way of thinking." Putin himself is a transition figure, a man formed by his experiences as a KGB officer. But after him, explained Peskov, comes a generation of Russians who don't carry the same baggage. They have traveled the world, seen things their parents could never imagine, looked at problems with fresh eyes.

To prepare for the next stage of the U.S. presidential campaign, try this thought experiment: Imagine the television footage of Barack Obama's first trip abroad as president -- the crowds in the streets of Moscow, Cairo, Nairobi, Shanghai, Paris, Islamabad. Now try to imagine the first visit by President John McCain to those same cities. McCain is a great man, and he would be welcomed with respect, deference, perhaps a bit of fear. Obama would generate different and more intense reactions -- surprise and uncertainty, to be sure, but also idealism and hope. Now tell me which image would foster a stronger and safer America in the 21st century.

Obama has liabilities as a candidate, but his inexperience paradoxically may actually bolster one of his core arguments -- that he would give America a fresh start.

The writer is co-host ofPostGlobal, an online discussion of international issues. His e-mail address isdavidignatius@washpost.com.