Also, I don't really think that Clark qualifies as "establishment" in anything like the sense that Clinton, Kerry, Biden et al do. I certainly don't see how he's any more "establishment" than Warner or Richardson, for example. To say the very least. Part of the establishment flirted with him briefly in 03-04 as the only apparent alternative to Dean, but they dropped him like a cold fish as soon as their boy Kerry surprised everyone by actually winning Iowa. Gore has also moved quite a ways away from the establishment over the past couple of years. I know that Clark, Gore and Feingold all appeal in different ways to many people who are dissatisfied with or infuriated by the current establishment, and while I can't see the numbers I would suspect that there is probably a significant correlation between support for these three here as well. That's a hypothesis based on substantial anecdotal evidence, anyway.

If you took a netroots poll in 2002 (after Gore said he wasn't running, let's assume), you'd have seen Dean on top.  You'd probably have seen Clark make a small blip.  Gephardt would have shown up fairly low, Lieberman nowhere, and Kerry moderately strong.  That poll would have been highly relevant and informative to those who knew what it meant.  Public polls at the same time, of course, if they even asked about Dean or Clark, wouldn't have bothered to report the insignificant results for those two.  They all would have showed Lieberman with a commanding lead, and Kerry and Gephardt as the likely second tier.  Those polls meant nothing.