“You’re not going to have time in January ’09 to get ready for this job.”

“If the position of president was a street, someone would have to hold Obama’s hand while he crossed it.”

Like John Kerry’s flip-flops or John Edwards’s haircuts, the foreign policy gaffes of Senator Obama have become a staple source of presidential campaign humor — so much so that the candidate himself has felt compelled to come up with counter-jokes. “To prepare for this debate I rode in the bumper cars at the state fair,” he told an Iowa audience on Sunday.

Yet given that his main rivals for the Democratic nomination include a one-term senator and another senator whose career, at least as an elected official, is only four years longer than Mr. Obama’s, maybe we should pause before laughing. After all, the barb in the jokes comes from the assumption — usually unquestioned — that there really is some specific, specialized, inside knowledge of foreign countries that some candidates have and some don’t, that is essential to holding the presidency. Is that true? Or, to put it in late-night talk-show language, do you really have to know the name of the Pakistani president to be a good American president?

Clearly you don’t have to know very much of anything about other countries to become America’s president, this not being a criterion that matters greatly to most voters. Famously, candidate George W. Bush couldn’t identify the Pakistani president — and thought Greeks were called Grecians — and he’d hardly traveled abroad. Candidate Bill Clinton had traveled abroad and knew the names of lots of international politicians, but he had never been required to use them, the governorship of Arkansas not being a job that involves much interaction with foreign leaders. By contrast, George H.W. Bush had plenty of foreign policy experience — as Central Intelligence Agency director and ambassador to China — none of which helped him when he sought reelection in 1992.

As for foreign policy decisions made in office, it’s far from obvious that any specific kind of experience has ever helped a president make good calls. Vice President Truman first heard that there might be some difficulties in relations with our Soviet wartime allies in April 1945, when Franklin Roosevelt’s death made him president — yet within months he had launched the Cold War. On the other hand, Lyndon Johnson had held national office for years before becoming president, but he still couldn’t cope with Vietnam.

In fact, there may be some sorts of experience that are actually detrimental to a potential president. I worry, for example, about Hillary Clinton’s much-vaunted travels as first lady: She came, she made carefully prepared speeches, she received polite applause. It won’t be like that if she’s president, and I hope she doesn’t think it will be. Other presidential candidates have been governors of large states or mayors of large cities and have bragged that they conducted mini-foreign policies of their own. Still, the world looks quite different — and Mexico seems a lot more important — from Austin, Sacramento, or Santa Fe, N.M., than it does from the Oval Office, while the verbal bombast needed to win votes in New York might not go down so well at a Group of Eight summit.

Other kinds of foreign connections could prove useful. Even aside from his specific beliefs, John McCain happens to be particularly good at speaking to — and arguing with — foreign audiences: The director of a German foundation recently complained to me that the American presidential campaign was spoiling his transatlantic conferences because it meant Mr. McCain couldn’t attend anymore. Meanwhile, Mr. Obama, with his African relatives and Indonesian childhood, would start his presidency riding an enormous wave of international goodwill. His differences from our current president — he’s young, black, with a more complicated background — would win him a lot of points in a lot of places, whether or not he knows the name of the Pakistani president — and whether or not he would bomb that country, as he recently seemed to imply he would.

In the end, most presidents do learn on the job: Mr. Clinton would probably never have predicted he’d contemplate bombing Belgrade, just as President Bush surely had never devoted much thought to Afghanistan. It’s not easy to predict whose particular set of experiences will suit which particular crisis and which weaknesses will prove fatal. But we can certainly entertain ourselves between now and November 2008 trying to guess.

Ms. Applebaum is an adjunct fellow at the American Enterprise Institute.