Wendell Willkie, 1939
A liberal Democrat in his early years, in 1932 Willkie took a break from corporate law to seek the Democratic Party's presidential nomination. After losing to Franklin Delano Roosevelt, he went into business for the nation's largest utility-holding company and grew into an outspoken opponent of Roosevelt's New Deal. In 1939 he joined the Republican Party, winning the presidential nomination in 1940 but taking a beating from Roosevelt in the general election. During World War II, Willkie did another 180, going on several diplomatic missions in staunch support of the President's wartime policies. By the time he decided to oppose Roosevelt in the 1944 presidential race, his seesawing loyalties had given Republican power brokers whiplash. They threw the nomination to Thomas Dewey instead. Undeterred, Willkie announced that he would create a new political party but died of a heart attack before the election.