Mutt without Jeff? Cornbeef sans cabbage? Unthinkable. Knebel without Bailey? Well, it's hard to tell the difference. It's still the same sort of push button/panic button story about politics from the Pentagon to the Hill, only this time one of the levers got stuck close to the beginning. The one called Idea. This is, namely, that a president of the United States, and he's got his button (The Bomb), has lost his other buttons. He's mentally disabled. No one suspects that Mark Hollenbach, a figure of great rectitude and a strong drive for excellence, is paranoid. Except Jim MacVeagh, a senator, whom he has just tapped as his next running mate. Jim, young, attractive, but lazy, has a family. He also has had, on the side, Rita, ""the urgency and solace of sex."" As the F.B.I. investigates this, at Hollenbach's instigation, Jim tries to persuade others just before a private Summit meeting. They remain unconvinced, think Jim is disturbed, and only Rita can supply the evidence until the President's unreasonableness becomes apparent elsewhere, and action, sadly missing throughout the book, is finally taken...Let's see now -- it could be Fredric March, Kirk Douglas, Ava Gardner. Oh, no, that was Seven Days in May. This isn't.