How do you pick a running mate?

We've seen two interesting example of non-traditional running mate selection in recent presidential elections, which may have caused some younger voters to forget the conventional thinking. The conventional thinking is that the running mate should "balance the ticket." This could mean a black choosing a white or a woman choosing man but mostly it meant a Northerner choosing a Southerner (Kennedy-Johnson) or vice-versa (Johnson-Humphrey, Carter-Mondale) or a Westerner choosing an Easterner (Nixon-Agnew, Reagan-Bush) or vice versa (Bush-Quayle). The first non-conventional choice of recent times came when a Southerner picked another Southerner -- from an adjacent state! -- (Clinton-Gore) which worked because they got along so well it was like watching a buddy movie. The other came when a candidate seen as lacking D.C. experience picked a veteran defense secretary and congressman (Bush-Cheney). Since Cheney was older and was advising Bush already, he was like a running mate-cum-consigliere. And the current campaigns? McCain is a Washington insider who can afford to, maybe needs to, reach outside the Beltway, as they say inside the Beltway, for someone who is young and dashing, a conservative Obama. Obama won't be choosing Hillary Clinton. She's been a target of humor, ridicule and criticism in Republican circles for years; with someone else Obama might get crossover votes, but not her. Sen. Chris Dodd, D-Conn., has been mentioned, but that won't happen: the chairman of the Senate Banking Committee took a cut-rate mortgage from Countrywide Financial. The Washington Post reported Tuesday that Obama aides have been vetting other possibles, including the governors of Kansas and Virginia as well as Sen. Joe Biden, D-Del., and former Sen. Sam Nunn, D-Ga. Biden and Nunn have this in common: they are international recognized experts on foreign policy. Most of the world's leaders know both of them. There has even been a little bit of talk of Obama considering a Republican. I doubt if a nominee of either party would do this other than in exceptional circumstances, since there was a case early in our country's history where that happened, and the president died in office, so the party in power actually changed. William Henry Harrison, the old general who died a month after his inauguration, was a Whig. His vice president John Tyler was a Democratic Republican, the ur-Democratic Party. Relax, I didn't remember, either; I had to look it up.