Being President of the United States can be lonely and daunting, and only a few people alive know what it's like firsthand. When a president leaves the White House, he enters one of the most elite clubs, which was established at Dwight Eisenhower’s inauguration by Harry Truman and Herbert Hoover. Its members are bound forever by the experience of the Oval Office and yet are eternal rivals for history’s favor. Yet the club members tend to have remarkable private relationships.