As political wonks everywhere chat endlessly about Obama's VP selection as though it is the most important thing in the world (it's not), we are subjected to a constant barrage of possible candidates. And as thos chattering class speculates about these candidates pluses and minuses, one of theme often emerges: McCain has better choices than Obama. Unfortunately, that idea only serves to strengthen one of the major narratives the McCain is pushing.
When you say Obama needs a VP who has knowhow in foreign policy or legislative experience or whatever, you are implying that Obama is weak in that area. Obama needs a VP who can strengthen his weakness. McCain needs a VP who can.. well what? Not make him look geriatric? This just plays into the McCain driven, media narrative that Obama has fundamental weaknesses that McCain does not... the narrative that sets up even when Obama has lead it's not large enough because Obama constantly needs to prove something. McCain on the other hand apparently simply needs to be McCain.
A VP selection shouldn't augment your weaknesses. It should augment your narrative. That's why Clinton's choice of Gore was so perfect. Gore backed what Clinton was selling. I don't know which possible VP candidate does the same for Obama. I'm trusting him to figure it out.