No offense, but you're proving my point for me. Dean had defining moments aplenty--from Gore's endorsement (how quickly we forget what a HUGE thing that was then), his leading in "superdelegates," his getting online funds to match those given to VP Cheney at a big dinner, the AFSCME endorsement, forgoing matching funds (very noteworthy), etc. The scream is NOW his defining moment, but up till then he was doing everything right, everything those who are advising Fred here on FR wish Fred would do. And look at what happened.
The things you listed were not defining moments. They were just things that happened. A defining moment can be quoted or viewed on film. Reagan’s “there you go again” is another one. George H.W. Bush looking at his watch was another. Al Gore stalking George W. Bush was yet another, as was Michael Dukakis’s tank ride. Nixon sweating, Ford saying eastern Europe wasn’t under soviet influence.