In reply to goat's question above, I reckon "the media" (which of course was first the print media, then came radio, then television) has always been "biased".
But back in the newsprint-only era, there was more of an "equilibrium of bias", with both sides having significant representation.
But starting in the 1920's, as Marxism first began to take hold in politics, that equilibrium began to shift leftwards.
And that shift turned into "a full tilt" by the 1980's. It's fallen completely over by now.
That's the way I see it.