At campaign stops over the weekend, former President Donald Trump, the Republican primary frontrunner, renewed attacks on immigrants with rhetoric that has prompted opponents to compare his rhetoric to that of Nazi leader Adolph Hitler.

"Donald Trump channeled his role models as he parroted Adolf Hitler, praised Kim Jong Un, and quoted Vladimir Putin while running for president on a promise to rule as a dictator and threaten American democracy," Biden-Harris campaign spokesperson Ammar Moussa said over the weekend. 

On Saturday, at a rally attended by thousands in Durham, New Hampshire, Trump said of undocumented migrants, "They're poisoning the blood of our country. They're coming into our country from Africa, from Asia, all over the world."

Although some Republicans, like Trump ally Sen. Lindsey Graham of South Carolina, brushed off the remark, Democrats weren't the only critics. 

Florida Gov. Ron DeSantis, who's running against Trump in the GOP presidential primary, did not denounce the remarks when pressed by reporters in Iowa on Monday, but he did call the rhetoric a "tactical mistake."

"Why are we in a situation where we're even having those discussions?" DeSantis said.

Another GOP primary opponent, former New Jersey Gov. Chris Christie had a more pointed reaction. 

"I don't know how you could take someone like that and say that they're fit to be president of the United States," Christie commented to "Face the Nation" moderator Margaret Brennan Sunday. 

At least one GOP congressman who has endorsed Trump criticized his rhetoric.

"I think immigrants are the lifeblood of our country, and it's important that we have immigrants," Texas Rep. Tony Gonzales said Sunday on "Face the Nation" in response to Trump's comments. 

Hitler used the term "blood poisoning" in his manifesto "Mein Kampf" to criticize the mixing of races, specifically, German blood being "poisoned" by Jews. 

The anti-immigrant rhetoric was not in the prepared excerpts of the speech that Trump's team sent to reporters ahead of the Durham event, but it is not the first time the former president has labeled the influx of migrants into the U.S. as "poisoning the blood of our country." 

"Nobody has any idea where these people are coming from," Trump said of migrants crossing the southern border in a September interview with The National Pulse, a right-wing website. "And we know they come from prisons. We know they come from mental institutions and centers, islands we know they're terrorists. Nobody has ever seen anything like we're witnessing right now. It is a very sad thing for our country. It's poisoning the blood of our country. It's so bad and people are coming in with disease, people are coming in with — with every possible thing that you can have."

CBS News has asked the Trump campaign for comment about the reaction to his remarks. 

In a November speech, also in New Hampshire, Trump again used language that echoed Hitler and fascist Italian dictator Benito Mussolini when he pledged to "root out the communists, Marxists, fascists, and radical left thugs that live like vermin within the confines of our country."

Trump continued, "The threat from outside forces is far less sinister, dangerous and grave than the threat from within. Our threat is from within."

In a December town hall in Iowa hosted by Fox News, Trump said he would not act like a dictator "except for Day One," if he were to be reelected. Fox News anchor Sean Hannity asked the former president whether he would use the presidency to "abuse power, to break the law, to use the government to go after people" several times. 

"You are promising America tonight you would never abuse power as retribution against anybody?" Hannity asked. 

"Except for Day One," Trump said. 

As he did in 2016, Trump has promised to radically shift U.S. immigration policy if he is re-elected in 2024, vowing to carry out mass deportations, to finish the wall along the U.S.-Mexico border, to end birthright citizenship for the children of undocumented immigrants, to introduce "strong ideological screening" for those entering the country and bring back his so-called "Muslim ban."

At an event in Reno, Nevada on Sunday, Trump reiterated those promises, pledging to move "massive portions of law enforcement" to militarize the U.S.-Mexico border.

"Just like three years ago, the invasion will end," Trump said. "We have to protect our own borders first."

Two of the three women the former president has been married to are immigrants who eventually became U.S. citizens. Former first lady Melania Trump participated in a naturalization ceremony last week. 

Camilo Montoya-Galvez, Aaron Navarro and Allison Novello contributed to this report.

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