The rise of the conservative alternative media can be traced back to the founding of the newspaper Human Events in 1944, Regnery Publishing in 1947 and National Review in 1955. But it did not become a mass phenomenon until the debut of Rush Limbaugh’s national radio show, in 1988, followed in 1996 by the launch of the Fox News Channel and the Drudge Report. Those still remain three of the most popular outlets on the right, but they have been joined by radio hosts such as Mark Levin and Michael Savage, authors such as Ann Coulter and Dinesh D’Souza, and websites such as Breitbart News, TheBlaze, Infowars and Newsmax.

The original impetus for these outlets was to offer a different viewpoint that people could not get from the more liberal TV networks, newspapers and magazines. But soon the alternative media moved from propounding their own analyses to concocting their own “facts,” turning into an incubator of conspiracy theories such as “Hillary Clinton murdered Vince Foster” and “Barack Obama is a Muslim.”

This might have been dismissed at one time as a fringe phenomenon. But it has moved into the mainstream now that the Republican presidential nominee has turned over his campaign to Stephen Bannon, executive chairman of Breitbart, which has become notorious as part of the white supremacist “alt right.” On Sept. 27, for example, Breitbart ran a vicious anti-Semitic attack on the historian and Post columnist Anne Applebaum. On Sept. 16, the site used a picture of a gorilla to illustrate an article about President Obama.