If John Kerry had been successful in his campaign for President we might now have the opportunity to read about all the "disastrous" mistakes the President and his organization made. As it turns out, we have a similar opportunity to read about Kerry's "disastrous" campaign.
In my opinion, as an amateur watching from the sidelines, the biggest mistake Kerry made was in basing his campaign on his Vietnam service. Using this as the cornerstone opened him up to a lot of criticism that ultimately hurt the public perception of his character. Without trust in Kerry the candidate, there wasn't much he could do to escape from that lack of trust. There is no logical position on an issue that will restore that overall sense of trust.
Overall, I don't think Kerry ran such a bad campaign. Ultimately, I believe it was his positions that hurt him in the voting booth, not anything specific about the campaign itself. The Boston Globe has done an excellent job of examining the Kerry campaign. The article does this examination by simply taking a look at how the decisions made, played out in the public eye.
The Globe article is titled On The Trail of Kerry's Failed Dream