Donald Trump’s new ad echoes the anti-immigrant campaign that doomed the California GOP.

Explaining the Trump phenomenon is difficult for anyone who doesn’t recognize that racism is still widespread in America, and harder still for anyone of the “both sides” bent, who can’t admit that its main political outlet runs through the Republican Party.

The idea that Trump’s popularity can mostly be explained away as misplaced economic anxiety, though, fails to account for the fact that Trumpism isn’t expressed as an economic program, but as a way to, as Greg Sargent put it, “keep the darkies out.”

This has as much to do with economic anxiety as the Pete Wilson ads of the Prop 187 era had to do with economic anxiety. In fact, the resemblance between the two, including darkened depictions of immigrants as invaders, is unmistakeable. Republicans are well aware that the Prop 187 campaign was the beginning of the California GOP’s long slide into oblivion. They’re also aware that wide swaths of the country are coming to look more like California than like Iowa every day. If bigotry were truly an impotent force in Republican politics, other candidates would be leapfrogging each other to denounce the ad, not as “unserious,” but as racist, and not just because racism is wrong, but because they want the national Republican Party to avoid the California party’s fate. Their indifference tells the whole story here.