Beauty isn't everything. Right?

American political campaigns are all about celebrity. The essential objective is to become more famous than one's opponent in a short amount of time. You do this with sly commercials, and pithy put-downs, and three-word mantras chanted by supporters, and, if you're lucky, by sheer personal attractiveness.

That's why I first thought the not-so-attractive John McCain had made a shrewd choice by picking Sarah Palin as his running mate: She's a great-looking woman with a wonderful smile. And if there's a single tenet upon which all Americans can agree, it's that great-looking people rule, particularly if they smile wonderfully.

But there's another tenet: Smart-sounding people also rule. Sometimes they rule even more -- say, after eight years of a president who has trouble putting a sentence together. Barack Obama's defining advantage has always been that he sounds very smart, even when his oratory soars into ephemeral realms and does not quite cohere. Hey, at least he's trying. Joe Biden always talks like he shouldn't have had that last martini, but his sentences hold up even when they're not strictly on message.

It's been a few weeks now, and I'm finally ready to conclude that Sarah Palin, good-looking as she is, doesn't sound very smart. She might have the brain of Steven Hawking behind those designer specs, but I have my doubts. Every speech is nearly identical to the one she gave at the convention; if I hear that "thanks but no thanks" line one more time, regarding the storied Bridge to Nowhere, I'm going to vomit. She doesn't give many interviews, and after the Charlie Gibson debacle, you can see why. It's as though memorizing that convention address didn't leave a lot of room upstairs for more facts. That's not a good sign. It wasn't that long a speech.

Now the McCain campaign is shuttling Mrs. Palin around to meet with various international figures, evidently deciding that if she's a little fuzzy about NATO or the Bush Doctrine, these guys can fill in some background. There she is with Henry Kissinger, of all people, whose mind seems to be elsewhere. Perhaps Paris in 1973. I don't know, perhaps his prostate.

This is not necessarily a bad thing. It can't hurt. If something sidelines McCain and she gets that phone call at 3 a.m., no doubt the chats she had with Hamid Karzai or the president of Colombia will be a source of inspiration. But there's something a little childish about it, too. It's as though she's cramming for finals, trying to get up to speed on the Magna Carta before being called upon by grumpy professor Biden. That debate is coming right up (Oct. 2), and he'll eat her alive if she once again shows up without her homework.

If I were going on national TV, I'd be cramming too. But then most of us wouldn't accept a vice presidential nomination if we really had no clue and no curiosity about U.S. foreign policy. This is what troubles me about Sarah Palin: I think she knows what she knows, and she doesn't deem it necessary to know more. Basing every decision on personal moral conviction may sound admirable, but as we've seen, it's no way to run a democracy. And it's no way to win an argument with Joe Biden.

It will be an interesting debate. I expect to cringe a fair amount. I'll go out on a limb and say it could be the defining point of the election.