There are lots of people who just don't respond to these calls. More and more are depending on cell phones only, and those are not even called in these polls.
You still don't get the point. Why would those NOT answering bias the poll EITHER way? Do only "conservatives" NOT answer? I don't think so. And if one who does answer claim to be a conservative what has changed? This is just another lame attempt to discredit the messenger because you do not like the message.