Here's an article about a provocative Harvard study, based on social media data:
https://www.newyorker.com/news/daily...-media-in-2016
Synopsis - it's mistake to assume the Left & Right in the US have a symmetry in news sources that feed their differing perspectives on reality.
Analyzing the rise of radical news on the left and right via accompanying ripples in social media, the study's investigators find a telling/disturbing trend:
2 examples: Alex Jones' Info Wars started a story about the Clintons operating a pedophilia operation, which got fairly widespread circulation within social media, culminated in the Rocket Pizza shooting. On the left, a reporter picked up on a revived lawsuit against Trump for having sex with a 13 year old. The suit was dismissed and the story had a very muted impact within social media.
There are no comparable idea factories on the left to InfoWars, etc, that create far-fetched stories that occasionally germinate up into more respected left leaning media like happens on the Right.
Maybe the biggest example of this phenomenon occurring on the Right is the Birther movement narrative - that eventually got great traction and had to be addressed by the State of Hawaii releasing Obama's "long form" birth certificate - which lingers on, like the various moon landing conspiracies, etc.
(An obvious response from the Right would be the Steele Dossier, considered a bunch of lies cooked up by the Clintons. The irony is this view was fabricated by Rightists as a "the victim sucked the bullet out of my gun!" kind of explanation/response to the actual Dossier, which seems to be holding up fairly well under investigation, as the explanations for Russian involvement slide from "never been to Russia" to "collusion isn't a crime" to "Hillary was far worse!".)
This study also explains why Trump claims "millions" are being denied free speech by Facebook & Twitter who are clamping down on troll farms and obvious false stories. (What he means is millions of his followers are being denied access to demonstrably false stories that feed their false narratives, forming the basis of their political world views.)