Over at TPMCafe, they're doing a roundup of "who won: Rahm Emmanuel or the netroots"? Leaving aside nonsense about Lieberman winning (he won because of Republicans due to a weak Republican candidate, nothing more)...
...neither won. Howard Dean won the election.
Why? Well, two reasons, really. One I already mentioned earlier: Dean's "fifty state strategy" ensured that there was already at least the beginnings of Democratic organizations in states that the Powers That Be had pretty much given up on. While that wasn't intrinsic to the success in many of the races, it was successful in bleeding Republican cash away from tight races so that they could defend safe seats, especially in situations like this one where "safe" is a relative term at best. This election shows that you have to at least make an effort to compete everywhere, because every race you leave uncontested is a race that they don't have to spend a dime to win, and incumbents tend to spend disproportionately.
The second reason is more ephemeral, but more important. Dean was anti-war. That isn't to say that an anti-war stance would have won in 2004--it wasn't tried--but what it did do is cement a connection between an anti-war position and at least part of the Democratic party. That matters, because if the Dems had had absolutely no anti-war candidates in the primary, we would have almost certainly seen alienation between the party and those who disliked the war. I'm not sure if they would have fled to, say, the Green party, but they may well have sat 2004 out, and been too disconnected from the triangulating Dems to really bother with 2006.
That they did find a candidate in Dean, though, means that they were forced to develop all those nice "netroots" tools that helped so much in 2006. The meetups, the online fundraising, the network of mutually supportive and resolutely partisan blogs that went beyond conservative-style repetition of talking points, the willingness to blend on-the-net and on-the-ground activism... all these things that the "netroots" contributed in 2006 were developed in 2004.
Without Dean, none of that would have happened. Without Dean, the Dems would probably just be happy right now with having reduced the Republican majority. Without Dean, there would probably be a divided left right now in the United States, just as there is in so many other countries. Without Dean, people would still think that Instapundit actually speaks for the blogger community.
So sorry, folks, but this is Howard Dean's party, and we're all just living in it. To our great good luck.