' Mr. Trump’s rise is actually a symptom of the mass media’s growing weaknessn controlling the limits of what it is acceptable to say. For decades, journalists at major media organizations acted as gatekeepers who passed judgment on what ideas could be publicly discussed, and what was considered too radical.We are in an era of rapidly weakening gatekeepers.... the Trump social media echo chamber is a world of wild falsehoods that you see only rarely in mainstream news outlets. The demagogy that Mr. Trump deploys was encouraged by the Republican leadership. In this election, the Republican Party hoped to engineer a controlled fire that would burn only political opponents — the current president, say, or Democrats as a whole, but not their preferred candidates. That’s a technique that may have worked in the era of mass media. Instead, it now rages, uncontrolled, on social media.'