As Obama starts the processing of picking his running mate, let's look at what criteria he should use.
I'm going the argue that the primary qualification we should look for in a VP candidate is loyal and vicious attack dog.
Yup, I'm putting helping Obama win the election above being a good alternative President. Not that choosing someone who would make a good President is unimportant. But Obama has to win for that to matter; and anyone who would not make a significantly better President than McCain would be a disastrous choice when it comes to campaigning anyway.
Why, of all campaigning skills, do we need an attack dog? Because we need someone who counterattack the Republican lie of the day: you know "Obama molests underage hamsters" or whatever talking point CNN picks up. Obama has good counterattack skills, but he has to limit his use of them because of the whole unity theme he has chosen. Now lots of people will voice counterattacks, but the VP is one of the few Obama surrogates with a good shot of being quoted.
That is not the only requirement, just (IMO) the most important. Other important criteria:
Whoever he chooses needs to be someone he can trust to be loyal to him. You don't want an attack dog who might prefer your opposition to you.
He needs to choose someone with a good record on feminism. It is not so much that a great feminist will win him a lot of votes, as that someone with a meh record could lose him votes within the Democratic base.
He is choosing a possible president when he picks his VP, so the person should be the best possible President with the appropriate campaigning skills. Someone who would be great at governing but would not shore up the Obama campaign is not a good choice.
Note that I've mentioned no names. That is because what criteria you choose really selects who you think will or won't make a good VP. Of course the VP choice is different from a lot issues we discuss. When we talk about health care or global warming or so on we hope to eventually have some effect on what happens - maybe not as individuals or in the short run, but as a community and in the long run. But we really are going to have no influence on who the VP will be. (Maybe I'm wrong, and if so the reason why would be an interesting comment.) But even without the ability to influence who the VP is it still worthwhile to discuss what makes a good VP pick, and who would pass various filters. So this post is not really an attempt to persuade anyone of anything. Rather I hope it will spark discussion of what the right basis is for picking a VP, with discussion of who passes various filters there but subsidiary to what those filters are.