Just some quick thoughts about the various political-debate sites I frequent.

Still the largest, still the least interesting. The software really holds them back a lot. It’s too hard to find good threads, and too hard to navigate within them. The self-moderation simply isn’t working either. I check this one every day but it’s two months since I posted there.
America’s Debate (no link, both by their request and my inclination)
Falling behind. The drive-by moderation – too heavy-handed in some cases, totally missing in others – is taking its toll. As with ETP I check every day, but now it’s a week since I’ve posted. Every time I check out a thread, I find that the same topic is already being done better somewhere else.
Struggling to reach critical mass. Again, the software is holding them back, though not as severely and the proprietor is trying to do something about it. The continued dominant presence of some uncouth nutjobs doesn’t help either.
U.S. Politics Online
Thriving, and becoming quite lively. There’s a good core group of posters, and the tone is generally mature. If current trends continue USPO could overtake AD some day. On some days they’re already there, by number of threads that I actually click to. I confess that I don’t post there very often, but that’s no reflection on them.
Whistle Stopper
The new king, IMO, and I don’t just say that because I’m on the staff now. WS has already overtaken both AD and ETP in activity level, and is on a path to overtake AD in number of users by mid-year. The reason is simple: everything I just said about USPO applies to WS as well, and they’ve done a better job of attracting users (via ads plus mass migration from Pravda). This is really where it’s happening, and where I do the vast majority of my own posting.

That’s really all there is to say. Natural selection and “market” forces are doing their thing. People are voting with their feet, or perhaps their keyboards.