I was just having a discussion with someone about what runs our country, funny you should post this. We've decided that OIL runs the US. But to opine on your question, I believe the media is a powerful influence of the general public. Not so sure about the effect it has on the operations of our government, however.
Everyone must believe in something. I believe I'll go kayaking
I don't have time for a long, in-depth answer at the moment but I do think that the media has a big influence on public opinion, and politicians really have no choice but to NOT ignore some of the consequences of that media influence if they wish to maintain approval ratings.
But also, certain "flavors" of media are popular because they air what people want to see and hear, so in an indirect way, I think they are also a reflection of popular opinion. I guess I see it as a symbiotic relationship of sorts, but the media certainly can help to influence and induce stronger public opinions and anger about various issues.