He really needs someone to impose a policy structure on his moral intuitions. He needs a very senior person who can organize a vast administration and insist that he tame his lone-pilot tendencies and work through the established corridors — the National Security Council, the Domestic Policy Council. He needs a near-equal who can turn his instincts, which are great, into a doctrine that everybody else can predict and understand.
Rob Portman or Bob Gates wouldn’t have been politically exciting, but they are capable of performing those tasks. Palin, for all her gifts, is not. She underlines McCain’s strength without compensating for his weaknesses. The real second fiddle job is still unfilled.