That is actually a form of psychological persuasion. Most people like to fit in and be agreeable with others in order to do so. This is a big point of study in psychology and sociology, one of the effects of which is peer pressure that you've no doubt heard a lot about. It stands to reason then that when fox news say that a large percentage of the country thinks a certain way, some people may start to say to themselves "Oh ya, I can see that point of view" whereas they would not have otherwise. It's actually pretty effective and not just on dumb people - there's a chance that it's been used at least subtly on any of you as well. Also, I'm sure fox news has a huge bias on the polls to get them to come out correctly and be able to label them as officially as they do. Actually since it's the circus that is fox news there is a pretty good chance they just make it up.