On the morning after the 1948 presidential election, the Chicago Daily Tribune's headline read "DEWEY DEFEATS TRUMAN." That's what the Republicans, the polls, the newspapers, the political writers, and even many Democrats had expected. But in the largest political upset in U.S. history, Harry S. Truman surprised everyone when he, and not Thomas E. Dewey, won the 1948 election for president of the United States.