The various TV networks conduct polls of their viewers, which of course consitute basically self-selected populations.

I watched the first of the three debates on PBS, the second on CNN, and last night on MSNBC. While the broadcast of the debate itself is identical on each network, the accompanying commentary is of course different in each case, giving each core-viewer audience pretty much what they expect. I would characterize the PBS audience as educated-elite, the MSNBC audience as left-leaning cynical, and CNN as about as mainstream as possible.

When, shortly after the debate, the audience is offered the opportunity to send a text-message vote or to log on to the network's website to express an opnion, it's not hard to predict how the results may or may not be skewed. However, despite the basic distinctions between the general characteristics of each audience-group, they are all TV audiences and therefore, HUGE numbers of people representing at least a LITTLE diversity.

In the first hour or so after the debate, MSNBC was reporting the results of various different polls, not only their own, and pointed out more than once that "even the FOX News poll" showed Obama as the winner. That must have been a different poll than the "Fox News text message poll" in which McCain got such overwhelming support ~ or maybe it was just an earlier count of that poll.

It should be no surprise that Fox News viewers would produce the most right-wing-favorable results. The early results of a Fox poll, any Fox poll, producing results favroable to Obama ~ THAT'S the anomaly!

I can't imagine how Guest from Sanity can assert, in relation to the FOX-viewer demographic, that "That'd be a pretty random cross-section of the population." I couldn't imagine any media outlet whose loyal viewers are less representative of a cross-section of the public than the rabidly neoconservative Fox.

My nominees for the most inclusive and therefore least biased of the post-debate polls would be:
AOL
CNN
the CBS poll of "undecideds only" (however they're able to identify and isolate undecided voters).