Arnold Palmer, circa 1966
Arnold Palmer had a five-stroke lead with four holes to play in the 1966 U.S. Open at the Olympic Club. Then Billy Casper went on a tear and completely erased Palmer's lead over the next three holes.
Palmer was able to tie Casper and force an 18-hole playoff scheduled for the following day. In the playoff, Palmer once again let a lead slip away. Palmer was up by two with eight holes to go but ended up losing the playoff to Casper 69 to 73.
This wouldn't be considered a collapse or choke had it not been for Palmer's seven-shot lead heading into the fourth day of the Open and having that lead disappear, forcing a playoff.
Palmer's failure is magnified by the fact that after regaining some momentum and forcing a playoff, he lost the playoff the following day.
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