Why Is Ron Paul Ignored by the Media?

So, in the latest poll from Public Policy Polling, Ron Paul leads the Republican field in Iowa. This, after a string of other candidates, popularly deemed the anti-Romneys, rose and fell. But the way all of those candidates were treated is very different from he way Ron Paul has been, that is, the other candidates weren't completely ignored. Sure, some of Paul's views are well out of the mainstream, but then so are many of the views of Michelle Bachmann, Rick Perry, Herman Cain, or Newt Gingrich. Ron Paul seems to occupy a different space in which he could never be seen as the anti-Romney. Is it because he is more libertarian and not mainline conservative? Is it a function of the GOP leadership dictating to the reporters whom they would have covered? Do the reporters just not like him personally? Is there another reason? Why is Ron Paul treated like he just doesn't exist?