Since the 1990s, when California Republicans’ numbers really began to dwindle, many of them have come to see the official embrace of a multicultural, multilingual California with porous borders and generous social services for immigrants, legal or not, as a mistake. And they have fought against it with ballot measures like Proposition 187 in 1994, which denied public services to illegal immigrants; Proposition 209 in 1996, which ended affirmative action in higher education; and Proposition 227 in 1998, which halted bilingual education in public schools. Each of them passed.

If those sound something like Trumpian policies, the echoes get even more specific: You could also say the Wall was born in California. Republican Rep. Duncan Hunter of San Diego, who served in the House from 1981 to 2009, was one of the first members of Congress to push for the construction of a border wall along the state’s southwest corner, before proposing in 2005 that a wall be built all the way across the border between the United States and Mexico. That ultimately led to the passage of the Secure Fence Act of 2006, authored by Rep. Peter King of New York, and the patchwork construction of a fence starting in San Diego. Construction of a prototype of the wall that Trump has called for could soon begin in Otay Mesa, a San Diego neighborhood near Sea World.

With little room for them in California politics—even the most successful recent Republican candidates, like Arnold Schwarzenegger, have been more moderate, Kousser points out—conservatives in the state began to take their ideas to the national level.