After the inauguration on Jan. 20, 1989, George Bush and I walked over to the east front of the Capitol to say goodbye to Ronald Reagan. A few moments later, as we watched the helicopter carry off the 40th president, I heard the 41st say quietly: “There goes a man who was very good to me.”

This was the end of Bush’s eight-year partnership with Reagan and the beginning of his partnership with me. And though ours would last for just one term, it could hardly have been more collegial, uncomplicated or free of tension. We were...