Your text states that the mass media can play a relatively positive role in influencing and shaping the public agenda through the following techniques: 

Setting the public agenda.
Framing issues.
Serving as a watchdog to guard against fraud and abuse. 

Choose one of the three methods above and explain how the mass media coverage informs the public about politics and public affairs in a positive way, and how it can also mislead and distort the truth.
In other words, can the media both enhance and undermine American democratic principles and values? Please explain.