Columbia Journalism Review – “The 2016 Presidential election shook the foundations of American politics. Media reports immediately looked for external disruption to explain the unanticipated victory—with theories ranging from Russian hacking to “fake news.” We have a less exotic, but perhaps more disconcerting explanation: Our own study of over 1.25 million stories published online between April 1, 2015 and Election Day shows that a right-wing media network anchored around Breitbart developed as a distinct and insulated media system, using social media as a backbone to transmit a hyper-partisan perspective to the world. This pro-Trump media sphere appears to have not only successfully set the agenda for the conservative media sphere, but also strongly influenced the broader media agenda, in particular coverage of Hillary Clinton. While concerns about political and media polarization online are longstanding, our study suggests that polarization was asymmetric. Pro-Clinton audiences were highly attentive to traditional media outlets, which continued to be the most prominent outlets across the public sphere, alongside more left-oriented online sites. But pro-Trump audiences paid the majority of their attention to polarized outlets that have developed recently, many of them only since the 2008 election season. Attacks on the integrity and professionalism of opposing media were also a central theme of right-wing media. Rather than “fake news” in the sense of wholly fabricated falsities, many of the most-shared stories can more accurately be understood as disinformation: the purposeful construction of true or partly true bits of information into a message that is, at its core, misleading. Over the course of the election, this turned the right-wing media system into an internally coherent, relatively insulated knowledge community, reinforcing the shared worldview of readers and shielding them from journalism that challenged it. The prevalence of such material has created an environment in which the President can tell supporters about events in Sweden that never happened, or a presidential advisor can reference a non-existent “Bowling Green massacre.”..”