On December 2, 2023, in the modest gymnasium of a community college in Cedar Rapids, Iowa, President Donald Trump addressed a raucous crowd of supporters. As he spoke about the enduring force of the movement he ignited in 2015, he paused to reflect on a man many had forgotten—but whose ideas are increasingly animating the rising generation of conservatives. “You know there was a man, Pat Buchanan, a good guy, a conservative guy,” Trump began. A sudden, collective cheer erupted from the left side of the stage—unmistakably youthful, unexpected in tone. “Wow! Young people, they know him,” Trump responded with...