Over the weekend, an 18-year-old man livestreamed himself shooting 13 people and killing 10. Within hours it became clear that the shooter’s intent was to kill as many Black people as possible. The suspect wrote online that he was motivated by replacement theory — a racist idea that white people are deliberately being replaced by people of color in places like America and Europe. What are the origins of this theory, and how has it become simultaneously more extreme and more mainstream?Guest: Nicholas Confessore, a political and investigative reporter for The New York Times. Want more from The Daily? For one big idea on the news each week from our team, subscribe to our newsletter. Background reading: Replacement theory, a fringe conspiracy fostered online and espoused by the suspect in the Buffalo massacre, has been embraced by some right-wing politicians and commentators.Here are our updates on the Buffalo shooting and the aftermath. For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.