It doesn’t take much under the best of circumstances to get Donald Trump boasting, so it’s no surprise that the Republican frontrunner used Thursday night’s debate in Cleveland to do some chest-thumping about his impact on the debate over immigration. When the topic was raised by moderator Chris Wallace, Trump was quick to trumpet his achievement. “So, if it weren't for me, you wouldn't even be talking about illegal immigration, Chris,” Trump exulted. “You wouldn't even be talking about it.”

Trump is exactly right. Immigration is a wedge issue Republicans hoped to avoid because it divides the party’s conservative base (who are leery of immigration reform) from its wealthy donor class (who are the big backers of reform). But Trump’s impact goes beyond the fact that immigration is a hot-button topic that took center stage during the two Republican presidential primary debates on Thursday. Trump’s lurid language of Mexican “rapists” entering America has polarized the GOP field. While candidates like Jeb Bush still defend immigration reform, conservative rivals hoping to stir up the base have adopted a much harsher language.

Trump’s impact is most clearly seen in Louisiana Governor Bobby Jindal, who during the earlier “undercard” debate among low-polling candidates made this startling pronouncement: “We must insist on assimilation—immigration without assimilation is an invasion…. They need to learn English, adopt our values, roll up their sleeves and get to work. I'm tired of the hyphenated Americans and the division.”

Jindal’s comments are startling because they go against the grain of most of the last century, when ethnic diversity was seen as perfectly compatible with membership in American society.

It’s true that a hundred years ago, during a Columbus Day speech in 1915, Theodore Roosevelt railed against “hyphenated Americans” declaring that there is “no such thing as a hyphenated American who is a good American.” Coming at the cusp of America’s entry into the First World War, his strident words were a forerunner to the wartime nativism that led to sauerkraut to be renamed the liberty cabbage and, more seriously, to mob violence against German-Americans. But Roosevelt's rhetoric was at odds with the already flourishing multiculturalism of an America where St. Patrick’s Day was a longstanding day of festivity, where newspaper columnists liberally sprinkled Yiddish in their prose, and where chop suey and pizza were part of the national diet. Contra Roosevelt, millions of loyal citizens had no problem thinking of themselves as Irish-Americans, Jewish-Americans, Chinese-Americans, African-Americans, among many other groups. A negative “assimilation” was sometimes forced upon these groups by state policies that forced a conformity to the dominant norms of white Anglo-Saxon society. But there was also the more positive assimilation of people from diverse backgrounds voluntarily coming together to create a shared culture. Much of American popular culture, ranging from Vaudeville to rock music, derives from this uncoerced fusion of ethnic traditions.

With his talk about the need to “insist on assimilation,” Jindal harkens back to the older and more negative form of assimilation, the one that involves assuming that immigrants are potential traitors unless bullied into accepting the cultural norms of their host country. The sinister implications of Jindal’s version of assimilation can be seen in his own life story. His parents were immigrants from India, but he’s gone out of his way to make common cause with white xenophobes. He’s one of the most stridently Islamophobic voices in the Republican Party. It’s possible that Jindal sees his status as a non-white son of immigrants as giving him a wider license to speak on these issues and to talk about immigrants in a way that would be dismissed as bigoted if it came from a white politician.

But Trump and Jindal are evidence that the arguments over immigration aren’t just based on economics or law enforcement, but also cultural anxiety about the changing demographic makeup of America. Trump keeps talking about the crimes committed by undocumented immigrants, a community that, according to the scholarly consensus, commits crimes at a lower rate than native-born Americans. In any case, the crime rate as a whole has been in steep decline for more than 20 years, so the success of Trump’s anti-immigrant rhetoric must have other sources. Jindal’s calls for a more assertive policy of forced assimilation is a window into what is really driving the immigration debate: worries about the displacement of the dominant white culture.