Kate Anderson Brower at The New York Times:

John F. Kennedy called on all three of his predecessors during the Cuban missile crisis, two Republicans (Herbert Hoover and Dwight D. Eisenhower) and one Democrat (Harry Truman). In 2005, George W. Bush sent his father on a trip around the world with Mr. Clinton, the elder Mr. Bush’s onetime rival, after the Indian Ocean tsunami. After Hurricane Katrina, the duo (whom Barbara Bush affectionately called the “odd couple”) raised money and their friendship became an enduring and reassuring sight.