First off, we can dispense with the right-wing talking point that I saw on Fox News while channel-flipping this morning, no John Kerry was not "too liberal" and no, he did not fail to be "centrist enough" (Read "right-wing enough").
The Kerry campaign survived the Republican dirty tricks and was good enough that a wartime, incumbent candidate had to settle for a mere 51% of the vote. Bush has no discernable mandate other than "Let's not allow gays to marry" as that was about the only publicly-declared difference between the campaigns that worked to get the Christian Right to the polls. The rest of the Bush supporters seem to have been voting out of fear and the old "don't change horses in the middle of the stream" idea.
Was Kerry our "great leader"? Did he run a "candidate-centric" campaign? Did he run his campaign so that it was all about him and his personality? Personally, I don't feel that he did. I felt this last campaign was very unusual in that Kerry was not the leader so much as he was the standard-bearer. He was the guy that "We The (liberal, leftist, progressive) People" handed off our standard to, the guy we entrusted with our flag to carry with him onto the field. Kerry was not our knight in shining armor, but our chosen champion, the fellow who represented us. I remember hearing lots and lots of complaints about him, but I heard very few ideas about how he could be doing a better job.
By far the most useful and profitable line of inquiry is "How could the campaign have done a better job of presenting our case"? I attended the big Kerry rally in Center City a few days prior to the election. It sounded okay to me and I cheered along with everybody else. Reading over various critiques, I can see now that Kerry's criticisms of Bush were scattershot and not very focused. As the German generals used to say: "But what is the schwerpunkt of the campaign?" That is, what exactly was our central point? What was our main critique? What was the one, burning question we could bring to our friends and co-workers and neighbors who claimed that Bush was the better candidate? Personally, my critique of the Bush Administration could be reduced to a sentence "Not only are these guys evil, not merely are they out to do awful things, they're incompetent on top of that!" Hmm, yeah, I can see how that particular sentence might not be a great talking point to bring to Mr & Mrs Joe Average.
One thing we can pester our politicians about is that we need to replace Terry McAuliffe, the money guy, with Howard Dean, a message guy. Once Bush had provided Democrats with a powerful set of messages (about what not to do), the money flowed in. Message is everything, money will take care of itself.