There's a meme going around Left Blogistan that the divide in the Democratic party is generational. The people with the good political sense are post-Reagan and those with bad political sense are pre-Reagan.
Not bad, except that the political sense parts are more messy than that. Having lived through Reagan, both as governor and as president, I can attest he is something of a watershed for Democrats. In both cases, we watched him preside over an assault on the gains created by the "old" Democrats. We saw him introduce a new rhetoric into the political consciousness, leaving behind the specific (and by then laughable) accusations of Communist Party membership that he so enthusiastically endorsed in the McCarthy era and broadened it to divide the nation into the loyal (pro-Reagan, pro-neocon) and the traitors (everyone else). He had the Soviet Union to use as his boogeyman. The fact that the USSR really was (and remains, but we dont' talk about that...) a threat to all life on earth due to its nuclear arsenal played no small part in legitimizing this approach.
Back to the generational stuff. I say that there is a generational divide, even if the "generation" is more mental than chronological. The netroots Dems are to mainstream Dems as Jerry Brown is to Pat Brown, both pairs divided by the altered reality of Ronald Reagan, the Movie.