A poll of 2.4 million people got the 1936 US election badly wrong

The Literary Digest mailed about 10 million ballots, got 2.4 million back, and confidently predicted Alf Landon would beat Franklin Roosevelt. Roosevelt won 46 of 48 states. Its lists came from phone directories, car registrations and its own subscribers, who were wealthier than average in the Depression, and the people who replied were not typical either. George Gallup called it right with a far smaller sample.

— Wikipedia contributors, The Literary Digest — 1936 presidential poll