Barack Obama and his advisers did him a lot of good last week when they picked Sen. Joe Biden, D-Del., as his running mate.

There’s a lot to be said for novelty in choosing a presidential candidate, and Obama provides it generously. It’s not simply that he happens to be black (though that is almost certainly an asset, and one not to be sneezed at). But he also fought his way up through the rugged politics of Southside Chicago to the U.S. Senate, and, after just three years there, offered himself as a candidate for the presidency of the United States.

That is not exactly a long record, nor is it spangled with any especially notable achievements while in office. He faces, moreover, an opponent in the general election — John McCain, R-Ariz. — who has served in the U.S. Senate for 22 years as a powerful member of the Armed Services and Commerce Committees.

So the selection of Biden adds serious and badly needed weight to the Democratic ticket. Biden has been in the Senate for 36 years, serving as a member (and for a time as chairman) of first the Judiciary Committee and then the Foreign Relations Committee. No one can challenge his expertise in these fields — certainly not his running mate.

Of course, there are limits to what a vice-presidential candidate, however distinguished, can add to a ticket. Once in office, he will have little to do with decisions in the fields of his authority, whatever those may be. But his very presence on the ticket, and then high in the prospective administration, would unquestionably benefit the combination.

That lends a certain extra interest to the decision McCain must soon make — his own choice of a vice-presidential candidate. Arguably, his best bet might be to choose a more novel running mate — a woman, say, or a black — counting on his own formidable record in office to compensate for any shortcomings one of these might have in terms of experience. We might, therefore, wind up with a Republican ticket consisting of a veteran white legislator (McCain) running for president, with a black or a woman for vice president, versus a relatively inexperienced black legislator (Obama) at the top of the Democratic ticket, teamed with a longtime senator (Biden) for vice president.

Such speculations are entertaining, but they may have relatively little to do with the choice McCain must soon make. With Russia’s recent move into Georgia much on the public’s mind, McCain might do better to pick a running mate with acknowledged expertise in the field of Middle Eastern affairs, or foreign policy generally, and let the Democrats be seen as the ones playing politics with such issues as race and gender.

In any case, as already noted, the Democrats have been wise to shore up the credentials of their ticket with such an undeniable authority on foreign affairs as Biden. In recent years, just for example, he has made no fewer than seven trips to Iraq. There is nothing quite like on-the-ground experience in these matters, and Biden can legitimately claim to have it.

McCain, happily for the Republicans, is equally at home dealing with Middle Eastern problems, and with foreign affairs generally. That gives him the opportunity to range more widely in choosing a running mate. In any case, the choice he makes will tell us a great deal about what he considers the vulnerabilities of his campaign, and perhaps even the prospects of the next administration. If he opts for a black or a woman, he will be saying that the Republican ticket must strengthen its appeal to these groups. If he chooses someone with acknowledged authority in foreign affairs, or in the Middle East in particular, he will be telling us that he expects that field to dominate the next presidency.

William Rusher is an accomplished author, former publisher of the National Review and former vice chairman of the American Conservative Union.