In choosing and displaying news, editors, newsroom staff, and broadcasters play an important part in shaping political reality. Readers learn not only about a given issue, but also how much importance to attach to that issue from the amount of information in a news story and its position. In reflecting what candidates are saying during a campaign, the mass media may well determine the important issues—that is, the media may set the “agenda” of the campaign.
McCombs, M. E., & Shaw, D. L. (1972). The agenda-setting function of mass media. Public opinion quarterly, 36(2), 176-187.https://s3.amazonaws.com/academia.edu.documents/45651357/The_Agenda-Setting_Function_of_Mass_Medi20160515-10629-xq1wt4.pdf?response-content-disposition=inline%3B%20filename%3DThe_Agenda-Setting_Function_of_Mass_Medi.pdf&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-