Matthew Yglesias highlights a bit of rationalization on the part of the DLC:
When last we checked, the DLC was against populism and very much against Howard Dean. In recent weeks, Deanophobia's won some big victories, so you'd think they might relax, but the trouble is that John Kerry and John Edwards seem to have been beating him with populism. The response -- a bit of revisionist history. It turns out, you see, that there are two kinds of populism.
The DLC is apparently arguing that there is "positive" populism, populism that uplifts people, while there is "negative" populism, populism that seeks to tear down the upper-classes. They then go on to basically say that their guys are only pushing the positive kind while the other guys (Dean, Gore, etc.) are doing the negative kind. Of course, in 2000 all we heard was that populism in general was a bad idea. But now that Kerry is succeeding by adopting (stealing) more populist rhetoric well they just have to find some way to differentiate things.
Of course, the fact that Dean might have been succeeding without Al From's blessing wouldn't have anything to do with his conclusion that Dean was pushing "negative" populism while their guys are pushing "positive" populism.
Nothing at all.