I will now describe, in one sentence, what many talented and thoughtful scholars have spent their careers studying. This is patently unfair, reductive and simplistic, but, for the sake of a blog post, we’ll be brief.
“Agenda setting” is the theory of the process where mass media can occasionally determine what the public thinks about. (Not the how, necessarily, but the what.)
Agenda setting is now (also) a public relations theory: How Dan Snyder Bought Off The D.C. Media