Donald Trump promises to be the most disruptive president of the United States since Franklin Delano Roosevelt was elected in 1932. Like Roosevelt, Trump was elected after a major economic slump that destroyed millions of jobs. Unlike Roosevelt who came to power at the height of the Great Depression, Donald Trump has an economy that is growing again and that is near full employment. But like Roosevelt, who was elected by those who were frightened by their sharp decline in economic fortunes, Trump was elected by those who have been left behind in the new economy, who have not recovered from the Great Recession. How likely is Trump to have this kind of transformative impact on the United States and on the world? Will Donald Trump return the United States to protectionism at home and isolation abroad? Will he break with the fundamentals of America’s postwar leadership? Or will he, as many Americans want him to do, “shake up” the American system and renew its role in the world? Conrad Black is a talented biographer who has written an authoritative biography of Richard Nixon and an acclaimed biography, Franklin Delano Roosevelt: Champion of Freedom. He was an early supporter of Donald Trump and predicted his victory when almost no one thought that Trump would win the election.