Nobody can hope to win without a positive message. Kerry really didn't offer one. His message was simply that he was not George W. Bush.
Kerry was severely handicapped by having to rely on a very dovish base in a time of war. This caused him no end of problems, and I don't know how he could have gotten around it.
Umm, if you went to the Kerry website, you could learn all about Kerry. If you went to the Bush website, you could also learn all about Kerry. Suppose you wanted to know about the guy who had been President for the last 4 years? Tough luck. See a problem?