David Frum: Do veeps matter? Who should McCain pick?

Some years ago, C-SPAN's Brian Lamb played a dirty trick on a journalist friend of mine. My friend was appearing on C-SPAN's"Washington Journal" to discuss recent events. If I remember right, my friend was expanding on the future of East Timor when Lamb abruptly shifted the conversation. It was, Lamb announced,"vice-presidents week," at C-SPAN: surely one of the network's most successful ratings stunts--and, more importantly, an opportunity for Lamb to deploy his notorious deadpan humor.

"Tell us which vice president of the United States this is," Lamb commanded. A look of concern flashed across my friend's face as a sad-faced man with a drooping mustache appeared on the screen. My friend confessed his ignorance."It's Garrett Hobart, McKinley's first vice president."

My friend struggled to return to East Timor. No dice. Later, Lamb cued a sepia photo of an elderly gentleman with bushy eyebrows tugging on an enormous cigar."See if you recognize this fellow." My friend drew another blank."That's John Nance Garner, former speaker of the House."

And so it went. In all the handicapper's excitement of the vice-presidential guessing game, it's easy to lose sight of the hard truth of American politics: It's rare that a vice-presidential choice makes any difference at all to the outcome of a race.

Presidential nominees have used vice-presidential choices to accomplish one or more of three main goals: unite their party, extend their demographic appeal, and balance some perceived personal deficiency. Thus Bob Dole chose Jack Kemp in 1996 to assuage the GOP right wing (ironically, the same reason that Gerald Ford had chosen Dole back in 1976). On the Democratic side, Jimmy Carter picked Walter Mondale in 1976 to reassure party liberals. The elder Bush opted for Dan Quayle in 1988 in hopes of wooing younger voters, much as Walter Mondale had chosen Geraldine Ferraro in an effort to mobilize women and George McGovern had hoped that Sargent Shriver would stanch his losses among Catholics. John Kerry chose John Edwards in 2004 to extend his appeal into the South and to balance his image as a scion of privilege....