According to a story on Thursday from the New York Times, Somali refugees arriving in the small Minnesota town of St. Cloud are facing bitter backlash from some white residents. While some in the town have welcomed their new neighbors, others are actively working against them, in part because of a particular racist conspiracy theory: "white replacement."

In the past 30 years, the non-white population of the town of 77,000 people has grown from two percent to 18 percent. That surge is comprised mainly of East African migrants, including a large number of predominantly Muslim refugees from Somalia. "I think of America, the great assimilator, as a rubber band, but with this—we’re at the breaking point," the general counsel of a conservative Minnesota think tank told the Times. "These aren’t people coming from Norway, let’s put it that way. These people are very visible."

This anxiety, that an influx of non-white, "very visible" immigrants will eventually overwhelm and displace white people in America, is a powerful driver for the far-right in America. And it often turns deadly. The man who gunned down 11 people at Pittsburgh's Tree of Life Synagogue—which works with HIAS, formerly known as the Hebrew Immigrant Aid Society, to support and relocate refugees—wrote online that he believed they were working to "bring invaders in that kill our people." In Christchurch, New Zealand, the man who murdered more than 50 people at two mosques described immigration as "assault on the European people," and wrote in a manifesto that, "This is ethnic replacement. This is cultural replacement. This is racial replacement. This is WHITE GENOCIDE."

The "great replacement," also known as "white genocide," is summed up by its name: a secretive cabal of elites, often Jewish, is trying to deliberately destroy the white race through demographic change in importing immigrants and refugees. Obsession with racial purity obviously goes far back, but the modern iteration of "white genocide" comes almost directly from The Turner Diaries, a racist novel self-published in 1978 by neo-Nazi William Luther Pierce, writing under the pen name Andrew Macdonald. The book is set in a dystopian America where white people have been disarmed and oppressed by non-whites. The book culminates in a white nationalist revolution led by a group called The Order, who go on to plan a global genocide against non-white people.

In The Atlantic, shortly before Donald Trump's election, J.M. Berger, an expert on extremism, estimated that The Turner Diaries had inspired at least 200 murders since it was published. Timothy McVeigh, the terrorist behind the 1995 Oklahoma City bombing, which killed 168 people, helped launch the novel to international fame when it was reported that his attack was styled on The Order.

According to Berger, Turner's appeal lies in the fact that it doesn't actually have any concrete ideology. The book is written for a racist audience, so it doesn't waste any time or space trying to convince the reader of anything. As Berger puts it,"The abandonment of 'why' empowers a singular narrative focus on 'what' and 'how'—the necessity of immediate, violent action and concrete suggestions about how to go about it."

There's another layer to the panic over demographics: the fear that birth rates for white people are falling all across western nations. The idea was partially popularized in a 2012 book by French philosopher Renaud Camus, and it's articulated in another white nationalist trope, the "14 Words": "We must secure the existence of our people and a future for white children."