Does modern media cover the news or create it?

Modern media covers the news, or at least the news they decide to cover. They also create the news by selectively covering what they decide to, covering the news in a way that might not be totally factual and not covering news that they decide not to cover, even though it might be something important.

Take as an example presidential primary campaigns in which several candidates are running. The media covers the news by covering the candidates. If they favor one or two of the candidates, they can cover their campaigns in a more positive light than others, give those candidates more coverage, give candidates they do not wish to win less coverage or put a negative spin on the coverage of those candidates, etc. By doing any of that, they are not only covering the news, but are creating news in that they are covering it in such a way as to bring about a desired outcome.