On November 3rd, 1948, one day after President Harry Truman defeated challenger Thomas E. Dewey, the Chicago Tribune made a slight error in their headline.

Okay, maybe it was a bit more than a "slight" error. It was a genuinely big one.

The LIFE Picture Collection, Getty Images

An error that a victorious President Truman didn't hesitate to exploit for laughs again and again in the days that followed.

From Wikipedia:

The erroneous headline of the Chicago Daily Tribune (which later shortened its name to Chicago Tribune) became ill-famed after a jubilant Truman was photographed holding a copy of the paper during a stop at St. Louis Union Station while returning by train from his home in Independence, Missouri, to Washington, D.C. The Tribune, which had once referred to Truman as a "nincompoop", was a famously Republican-leaning paper. In a retrospective article over half a century later about the newspaper's most famous and embarrassing headline, the Tribune wrote that Truman "had as low an opinion of the Tribune as it did of him".

For about a year prior to the 1948 general election, the printers who operated the linotype machines at the Chicago Tribune and other Chicago papers had been on strike, in protest of the Taft–Hartley Act. Around the same time, the Tribune had switched to a method in which copy for the paper was composed on typewriters and photographed and then engraved onto the printing plates. This process required the paper to go to press several hours earlier than usual.