It's been almost a century since America had an ex-President who occupied such commanding ground. Bill Clinton is full of energy, full of ambition, full of other things. What Clinton will do next is an always interesting question, the more so now, when there is so little left that he hasn't done. A man who's devoted his life to scaling a height has run out of summit. Will he descend like Moses? Fall like Teddy Roosevelt? Jump? Be pushed? Or will Bill Clinton keep climbing past the peak, in the manner of a cartoon character, on into the air? For...