Wendell Willkie never held a public office, yet he nearly became president of the United States. A registered Democrat until the fall of 1939, he captured the Republican party's nomination less than a year later. It was, by all accounts, a meteoric rise--to win the nomination Willkie defeated such party stalwarts as Thomas Dewey, Robert Taft, and Arthur Vandenberg. These Republican front-runners had been insisting that the war in Europe wasn't a national concern since two oceans protected the U.S. from the aggressors, while for months Willkie had warned of the danger of a Europe controlled by...