Willkie was widely known in political circles and among newspaper reporters as a womanizer. In fact, he made no attempt to hide his affair with Irita Van Doren, the popular book editor of The New York Herald Tribune. She was divorced and they lived together despite the fact that Willkie was married. They traveled together and were invited as a couple to friends' homes. When it looked like Willkie, who was president of a utility holding company, might actually become a presidential candidate, advisers urged that his paramour be kept in the background until after the election.
Willkie resented the hypocrisy of politics and refused. He believed his private life was his own. After the nomination, when a reporter confronted Willkie about the affair, he is said to have replied, "I am in love with another woman — and I don't intend to apologize for that and pretend that it isn't so. If you print this story, my campaign for the Presidency is probably over. But that is your decision. I have made mine."
The story was never printed but a Broadway play, State of the Union (1945) by Howard Lindsay and Russel Crouse, was loosely based on Willkie's affair. It opened after Willkie's death and ran for 765 performances. The play won the Pulitzer Prize for Drama. Frank Capra directed a 1948 film adaptation.
In 1944, as Willkie began seeking the Republican nomination again, he published a book titled An American Program. It was a collection of articles he had written for various newspapers on his vision for the nation plus critical analyses of the Republican and Democratic platforms. After losing in the Wisconsin primary, Willkie withdrew from the race. He never held public office.
Willkie was the subject of two biographies and other books, including Willkie (1952), Dark Horse (1984), The Republican Party and Wendell Willkie (1960, reprinted 1981), Roosevelt and Willkie (1968), Wendell Willkie: Hoosier Internationalist (1992).