At an Iowa campaign rally on Tuesday, former President Donald Trump doubled down on his characterization of immigrants as “poisoning the blood” of the nation, a remark that has drawn backlash from his opponents and echoed the justifications of Adolf Hitler for the Holocaust as he embraces a more authoritarian image and agenda.

President Joe Biden, his campaign, civil rights groups and historians have not been shy in making the comparison, typically used in American politics prior to Trump’s rise for hyperbolic attacks on ideological foes. Now, they argue, the man dominating the 2024 GOP presidential primary is embracing the fascist and racist rhetoric of Nazis and other authoritarian regimes.

“The language he uses reminds us of the language coming out of Germany in the ‘30s,” Biden said at a Maryland campaign fundraiser on Tuesday. “He has called those who oppose him ‘vermin.’ And, again, this weekend, he talked about ‘the blood of our country’ is being poisoned.”

Within a couple hours of Biden’s remarks, Trump took the stage in Waterloo, Iowa, to defend his comments that immigrants are “poisoning the blood of our country” in a New Hampshire speech over the weekend.

“They’re ruining our country. And it’s true that destroying the blood of our country. That’s what they’re doing. They’re destroying our country,” Trump told the crowd at a convention center, standing in front of two Christmas trees with “Make America Great Again” toppers. “They don’t like it when I said that. And I never read ‘Mein Kampf.’”

In “Mein Kampf,” Hitler’s manifesto, he wrote, “All great cultures of the past perished only because the originally creative race died off through blood-poisoning.” His obsession with blood purity and the superiority of the so-called Aryan race came to define the Nazi state and lay the foundation for the Holocaust, which killed six million Jews and millions more who were perceived to be tainting the blood of the Reich.

“The Nazis made the fear of blood pollution of their master race and their civilization a foundation of their state,” New York University professor Ruth Ben-Ghiat, an expert on fascism, said in a video posted on social media. “His campaign is really clear about what they want to do to immigrants. They want to deport them en masse. They want to detain them. They want to have swept in cities — many, many Americans will see immigrants being rounded up and treated badly and violence.”

Trump has promised “the largest domestic deportation operation in American history,” and the New York Times has reported that should he win back the White House, he plans to build large camps to detain people who enter the country illegally or to seek asylum.

Yale professor Jason Stanley, who authored the book “How Fascism Works,” told Reuters Trump’s tactic of repeating the dehumanizing language was to normalize the concept for his supporters, adding, “This is very concerning talk for the safety of immigrants in the U.S.”

Biden and experts were not alone in drawing the comparison. The League of United Latin American Citizens, one of the nation’s largest Latino civil rights organizations, and the antisemitism-combating Anti-Defamation League denounced Trump’s initial blood poisoning remarks in a statement on Tuesday.

“Donald Trump’s remarks in recent days accusing immigrants of ‘poisoning the blood of America’ are reminiscent of the language of Adolf Hitler and the Nazi regime,” said Domingo Garcia, LULAC’s national president, labeling Trump’s rhetoric as hate speech. “Trump’s words very intentionally create hatred of the other and are nothing more than fear-mongering. They play to the lowest and most sinister human emotions to incite hatred and cause harm or worse to innocent men, women, and children.”

ADL CEO Jonathan Greenblatt noted that “such nativist talking points have the potential to cause real danger and violence,” including mass killings by white supremacist gunmen in recent years.

“We have seen this kind of toxic rhetoric inspire real-world acts of violence in places like Pittsburgh and El Paso. It should have no place in our politics, period,” Greenblatt said. The worst attack on Jews in U.S. history took place at a Pittsburgh synagogue in 2018, when 11 worshippers were killed by an antisemitic gunman inspired by conspiracy theories about whites being replaced by nonwhite immigrants.

And in 2019, a white nationalist targeted Hispanics and murdered 23 people at an El Paso, Texas, Walmart. Other attacks inspired by hatred of immigrants and minorities claimed 51 Muslim worshippers at mosques in New Zealand in 2019 and 10 more at a grocery store in a predominantly Black neighborhood in Buffalo, N.Y., last year. 

Sen. J.D. Vance, R-Ohio, said it was “objectively and obviously true” that unauthorized immigrants are poisoning the blood of the country, according to leaked audio of an interview with Vance conducted by an Associated Press reporter published by the right-wing outlet the Daily Caller. Vance attacked the reporter for drawing a comparison between Trump and the historical rhetoric of European fascist in the World War II era. He argued she shouldn’t assume “that Donald Trump is talking about Adolf Hitler.”

“It’s absurd. It’s absurd. Why do you think Donald Trump’s language is targeted at the blood of the immigrants and not at the blood of the American citizens who are being poisoned by the fentanyl problem,” Vance said, claiming Trump was referring to the epidemic of drug overdoses and addiction. “To take that comment and then immediately assume that he’s talking about immigrants as Adolf Hitler talked about Jews is preposterous.”

Trump did not mention drugs or fentanyl at his Tuesday rally, and in his Saturday speech, he only spoke of them briefly and nearly a half hour after his “poisoning the blood of our country” statement. Instead, he said immigrants were criminals, mentally ill, diseased and terrorists.

“Mussolini actually talked about rats who should be killed because they were bringing infectious diseases and communism into Italy,” Ben-Ghiat said.

But several other Republican lawmakers condemned Trump's rhetoric, including Maine Sen. Susan Collins, R-Maine, who the remarks “horrible."

“I thought that was horrible, that those comments ... just have no place, particularly from a former president," she told reporters. "They’re deplorable.”

South Dakota Sen. Mike Rounds slammed Trump’s “unacceptable rhetoric,” though he attempted to point fingers at the Biden administration’s immigration policies.

“I think that that rhetoric is very inappropriate, but this administration’s policies are feeding right into it,” Rounds said, per NBC News. “I disagree with that. I think we should celebrate our diversity ... unfortunately, that type of rhetoric is what happens when you don’t have a border policy that works, and it just simply feeds that type of poor, unacceptable rhetoric.”

Sen. John Thune of South Dakota, the No. 2 Senate Republican, told CNN “my grandfather is an immigrant, so that’s not a view I share.”

Former Attorney General Bill Barr, who helped implement Trump’s first-term anti-immigrant policies, said on CNN on Tuesday the comments had “racist overtones” and that Hispanic immigrants made good military service members and were a “boon” for the U.S. because they “come out of the Western tradition, they’re religious people, good family people, in general.”

And Senate Minority Leader Mitch McConnell, R-Ky., told reporters that “it strikes me it didn’t bother him when he appointed Elaine Chao Secretary of Transportation.” An immigrant from Taiwan, Chao is married to McConnell, and Trump has frequently targeted her with attacks centered on her heritage.

Florida Gov. Ron DeSantis — one of Trump’s rivals in the 2024 GOP primary who has received his own criticism for his rhetoric on race and immigration — didn’t express concern with Trump’s sentiment but said on Tuesday in Iowa using the phrase was a “tactical mistake” that gave Democrats ammunition to attack Republicans.

On average, Trump leads DeSantis and his other challengers by over 50 percentage points in national polls and dozens of points in the all-important early primary states of Iowa, New Hampshire, and South Carolina. 

The Iowa caucuses are on Jan. 15, 2024.