The first grave mistake of Bush's presidency was rushing toward military confrontation with Iraq. It took his presidency off course and greatly damaged his standing with the public. His second grave mistake was his virtual blindness about his first mistake, and his unwillingness to sustain a bipartisan spirit during a time of war and change course when events demanded it.
At page 301 of the book, McClellan describes the scene when he talked to Bush in the Oval Office about the fact that he was leaving as his press spokesman. He says that tears were streaming down Bush's cheeks as they talked. I wonder if that is because he forsaw that his old friend was about to write a book about what really happened in the White House.