One of the Important power of the media is the ability to set what the public believes to be be the reality. This theory was proposed by Dr. Donald Shaw and Maxwell McCombs and just like it is given in the first statement in the question, agenda setting by the media is used to shape the issues people think about.
Another Important power of the media is framing. Framing is used by the media to influence how Americans think about the issues at hand. These two tools(that is agenda setting and framing) are important tools used by the media during political events.