A newspaper printed the wrong election winner on its front page

On election night in 1948, the Chicago Tribune went to press early because of a printers' strike, trusting polls and early returns that showed Thomas Dewey beating President Harry Truman. Its headline read 'DEWEY DEFEATS TRUMAN'. Truman won, and two days later he was photographed grinning as he held the paper aloft, one of the most famous images in American political history.

— Wikipedia contributors, Dewey Defeats Truman — Chicago Tribune, 3 November 1948