The challenge for Obama is that he has so many weaknesses to cover with a VP pick.
Most of the time it's pretty obvious what vulnerability needs tending, and the VP slot can start to address it. For example, if you've got a Northern Democrat, a Southern Democrat can balance his geographic appeal. If you've got someone strong with the cities, get someone strong with rural areas as a complement. If you've got a very liberal Democrat, a more centrist one can balance his political appeal. If you've got a candidate without military experience, a VP with military experience will cover that. If you've got a candidate who has unusually little big-time political experience, a real Washington heavy-hitter can cover that. If you've got someone who lacks executive experience, pair him with a governor or someone who had a major role in some prior administration.
That's in addition to the general desire to have a tireless campaigner, someone who'll do well in the VP debates, someone who is comfortable in the role of attack dog, someone who is a strong fund raiser, and someone who is demonstrably comfortable in the role of second fiddle to the president.
With Obama's you've got the perfect storm. You've got a Northern, liberal, urban Democrat with no miltary experience, no executive experience, and some of the least big-time political experience ever for a major party nominee. There's simply no option as VP who can cover up all Obama's many vulnerabilities simultaneously. Whoever they pick, the contrasts with McCain are going to be major and unflattering. And picking someone gets all the tougher when you also try for that tireless campaigner and strong debater with an attack-dog mentality, much less one who is comfortable taking the second chair and knows how to rake in the dollars.
Clinton may be about as close as they can reasonably get to a good complement. She's stronger than Obama with working class whites, rural residents, Hispanics, older folks, and battleground states, all of which will be critical in November. She also has considerably more big-time experience than Obama, including a prominent role in a hugely successful Democratic presidential administration. She does nothing for him on the military front, but that may be a lost cause up against McCain, anyway.
Clinton is a relatively good complement for Obama, and she has the other traits people want in a VP. She's not quite as good a fundraiser as Obama, but she's still among the best ever. She's not quite as willing to go with the low blow as Obama, but she certainly can play the attack dog when it's called for. She's every bit as much of a tireless campaigner as Obama. She's a much better debater than Obama. And she happily took the backseat to the President for eight years during the Clinton administration. How much more would you want from a VP?
I don't doubt that Obama has spent so much time swooning over his own press clippings that he won't have the character to offer the VP slot to Clinton. But it's the smart move, and the right one for his party and this country. I hope he proves me wrong about his arrogance. Time will tell.