No one really knows why the Dean campaign stalled out. I've heard Joe Trippi speak compellingly about what the mainstream party people did to sabotage it.
Chris Nolan publishes a really good political blog, examining a lot of issues better than I've seen elsewhere, very recommended. She knows what she's talking about, as opposed to my own screwing around.
She begins to explore the issues of the Dean campaign in Operators, Give Me Information, opening questions and directing you to explorations of those issues. The links are real valuable in themselves.
Just to be sure, I think the Dean campaign was a success, in that it contributed a lot to the evolution of politics… but there's a lot more needed.