These charts are from a survey done by the Pew Research Center between March 13th and 27th of a random national sample of 4,151 adults, with a 2.7 point margin of error. It shows a growing partisan divide over the media.
About 89% of Democrats think the media's reporting keeps politicians from doing things they shouldn't do, while only 42% of Republicans feel that way -- a huge gap of 47 points. There is also a gap, albeit smaller, in the perception that the media favors one candidate (or party) over another -- with 87% of Republicans saying that and 53% of Democrats (a 34 point gap).
There is also a gap on whether the media does very well/fairly well in keeping citizens informed. About 88% of Democrats believe the media does well, while only 69% of Republicans believe that -- a gap of 19 points.
It seems that Donald Trump's repeated attacks on the media is having an effect -- at least among Republicans.