The conspiracy theory, which has roots in France and also targets Jewish people, has become a common far-right ideology and has been connected to multiple mass shootings carried out by white supremacists, including the 2018 Pittsburgh synagogue shooting, 2019 mosque shootings in Christchurch, New Zealand, and the 2019 shooting at a Walmart in El Paso, Texas.
Although the Buffalo attack is still under investigation, the references to replacement theory in the document and its echoes in right wing media show how a racist and anti-Semitic conspiracy has been mainstreamed. Its central ideas are now promoted not just by violent extremists, but by right wing media personalities like Fox News host Tucker Carlson.
"I mean, this is really ugly stuff, and it's really extremely similar to what is in this guy's manifest," said Matt Gertz, a senior fellow at Media Matters for America, a nonprofit media watchdog that has tracked the spread of replacement theory on Fox News.