How  media in politics has evolved in US history

How  media in politics has evolved in US history, particularly with the recent explosive growth of the internet and social media?

Does the mainstream media generally achieve its ideal of objectivity and neutrality? Or is it inherently plagued by certain biases?

Does ideology (left-liberal or conservative) tend to color what is reported (and how) and what is not? Does the corporate bottom line lead to “infotainment,” sensationalized negative news, “soft news,” and superficial sound bites dominating mainstream media reporting?