Americans' trust in the media "to report the news fully, accurately and fairly" has been dropping fairly steadily for quite some time. See Public trust in media falls to historic low. Those days when viewers trusted Walter Cronkite to be unbiased are long gone, thanks in some part to Cronkite's own eventual outing as a hard core Democrat.
That people have lost trust in the institution isn't news. What's noteworthy is the presidential election years, 2000, 2004, 2008, 2012, and 2016. The trust takes a decided dip in each of those years. Check it out in interactive chart at the aforementioned article. The image below is a JPG snipping tool capture.
It should be no mystery why trust drops in those years. As the msm piles on to support one candidate against the other, their bias is more obvious than they probably realize.