most disappointing prersidential candidate of the last 50 years?

[Robespierre's Jaw]

I agree with Walter and say Nelson Aldrich Rockefeller. He probably would have gotten the '64 GOP Nomination thanks to a victory in the California Primary, however that wasn't to be the case all because he married a woman who was about 20 odd years younger than him. He would have done better than Goldwater against LBJ in '64 but still he wouldn't have been elected President.

[Robespierre's Jaw]

Ed Muskie was a disappointment when he ran in 1972. He was the clear frontrunner, he was a Democratic Senator and Governor from a then traditional Republican state. Then he blew it when he cried in the snow over an article attacking his wife or something to do with his wife. Then come New Hampshire Primary, he wins but not by the margin his anticipated.

[Robespierre's Jaw]

I would also say Governor Michael Dukakis in 1988. After the Democratic National Convention in Atlanta, the Dukakis/Bentsen ticket had a massive 17 point lead over the then incumbent Vice President George H.W. Bush. Then his campaign went down hill after those Willie Horton commercials and his response about Kitty Dukakis' being raped in the Presidential Debates.