The 1904 Olympic Marathon
You can't really fault the multiple instances of cheating during the 1904 St. Louis Olympics marathon since it was basically a 26-mile Benny Hill skit that included one top contender being chased off the course by wild dogs, and another running in wingtips and trousers. The original winner of the race was Fred Lorz, a future Boston Marathon winner who led for nine miles before dropping out due to cramps, and then, after accepting a ride to the stadium, figured he'd play a joke on the crowd and jog triumphantly to the winner's circle. He even received the champion's wreath from President Teddy Roosevelt's daughter before admitting to his hitchhiking. So instead, American Thomas Hicks, who was kept upright for ten miles by regular doses of strychnine and brandy, and who was effectively carried across the finish line by his coaches, won the gold because no one wanted to see the French second place finisher walk away with the victory.