I don't think I'd want to visit, much less live in, the parallel universe that hosts a President. That's the universe where if he makes the wrong call on fiscal policy, a million more people lose their jobs, or the wrong judgment about an enemy, and thousands lose their lives. Presidents rise or fall according to how they handle a crisis an invasion, a depression, a massive oil spill but they seldom get credit for the crisis they prevent, especially since they can't prove it would have happened in the first place. As Barack Obama weighs his options in Afghanistan or where and how hard to shock the economy in hopes of finding a pulse, as he watches poll numbers slip and confidence slide and 7 in 10 people say his economic rescue attempt has made no difference, there's a shadow President over in the alternative reality who is wondering, Just where would we be now had I not administered CPR when I walked in the door?
Scratch a President's skin and you'll find someone who is nearly as proud of what doesn't happen as what does. Sometimes the biggest part of the job is foreseeing and forestalling, or keeping bad things from being worse; not much in the way of credit for that, but a lot of time spent and sleep lost. When the weight of office is finally off their shoulders, this is often what former Presidents remember. Though eternally popular personally, Eisenhower endured the condescension of some in even his party who dismissed him as the custodial President of a sedated country. He knew otherwise: knew how many times in the course of his two terms his advisers urged him to dispatch the Marines, whether to Vietnam, Suez, Hungary, Quemoy and Matsu advice he resolutely resisted in his hunt for a better way. "The United States never lost a soldier or a foot of ground in my Administration," he argued in retirement. "We kept the peace. People asked how it happened. By God, it didn't just happen, I'll tell you that."
In a President's parallel universe, even normal calculations collapse under pressure. Risk is supposed to equal probability times consequences. Do I dare leave home without an umbrella? There's a less than even chance it will rain, the umbrella is heavy, it doesn't really matter if I end up getting wet, so I leave it at home. But now imagine you are in the White House, weighing the risk of confronting your enemy over Cuba or Vietnam, wondering if that would unleash a nuclear holocaust that would mean the end of civilization as we know it. Now the math goes out the window: no risk could be worth an infinitely bad outcome. But Presidents can't think that way, or they would be held hostage by fear. So they have to pick their way toward solutions, commuting back and forth to the alternative reality where they glimpse what could happen if things don't go as planned.
Thus did Lyndon Johnson, retired to his ranch in Texas, brush back his aide and later biographer Doris Kearns Goodwin when she suggested there might have been some other road to peace in Southeast Asia. "I will not let you take me backward in time in Vietnam," he growled. "Fifty thousand American boys are dead. Nothing we can say will change that fact. Your idea that I could have chosen otherwise rests upon complete ignorance. For if I had chosen otherwise, I would have been responsible for starting World War III." He knew the price he was paying, personally and politically, including the cost to the Great Society vision he cherished. "Do you know what it's like to feel responsible for the deaths of men you love? Well, all that horror was acceptable if it prevented the far worse horror of World War III. For that would have meant the end of everything we know."
Every President lives with his own version of this. Gerald Ford's aides sat mute as he explained his plan to pardon Richard Nixon and spare the country prolonged agony. "The President's logic was unassailable," one adviser recalled, "yet I felt as if I was watching someone commit hara-kiri." George W. Bush lives with the legacy of Abu Ghraib and waterboarding and the costs of making "hard calls" but left office able to say, we were not successfully attacked a second time on my watch, and who in the fall of 2001 would have predicted that?
This may be one reason Bush has said many times that President Obama "deserves my silence." Every President will have his critics, but in the modern age, they seldom include his predecessors. All Presidents are fellow travelers in the parallel universe, where the terrain of regret looks very different and where there is hardly ever such thing as a perfect outcome.