Have you watched Tucker on Twitter? If you're here, then probably not, which means you might not know this phrase. The “great replacement” theory comes from a French guy named Renaud Camus who self-published a book in 2011 called Le Grande Remplacement with a 3.8 on Goodreads. It says that wealthy Jews (e.g., George Soros) are conspiring to import racial minorities into the U.S. to weaken the voting power of white Christian men.
The ‘great replacement’ also implies Jews (who are 2.4% of the U.S. population) are trying to supplant Christianity and Christians (who are 63% of the U.S. population) with a “Judaized” way of life (which, in our experience, just means good bagels and Curb marathons, but I guess some people don't want that?). Or, it’s framed through other dog whistles, like globalists vs. real Americans. Jews, apparently, are also trying to replace the U.S. Constitution with Jewish religious law (Halakhah). The end goal of the Jewish people, according to this theory? White genocide, aka what happens every season on the finale of White Lotus.
In short, the ‘great replacement’ is just a repackaging of old, pre-existing Jewish conspiracy theories — that Jews control the banks, control politics, and hate Christians – with the addition of modern immigration patterns as “proof.” The real fear behind this – and behind globalism, ‘people coming for jobs,’ and other dog whistles – is the worry of being treated as badly as Jews and immigrants have been historically treated (if white Christians were to be the minority).
Unfortunately, the “great replacement” is widely believed and has been used by white supremacists to justify the murder of Jewish people, Black people, Hispanic people, Muslim people, and others. It's…very bad and very scary.