Donald Trump's history with Adolf Hitler and his Nazi writings: ANALYSIS

At his campaign rally in Iowa this week, Donald Trump once again broke new ground, becoming the first leading presidential candidate to find it necessary to insist he had never read the most infamous book of the 20th century.

"I never read 'Mein Kampf,'" Trump said, referring to Adolf Hitler's manifesto ("My Struggle") that provided the philosophical basis for Nazi Germany and, ultimately, the murder of more than 6 million Jews in the Holocaust.

This was the first time Trump had invoked Hitler's name and the title of his memoir at a political rally, but there have been multiple reports over the years of Trump expressing a keen interest in, even admiration for, Hitler's rule over Nazi Germany.

In the past, he's actually acknowledged owning a copy of the book.

Trump's denial that he had read Hitler's memoir came after he has made a series of incendiary remarks in recent weeks referring to his political opponents as "vermin" and saying illegal immigrants are "poisoning the blood of our country."

There's no question that language echoes that Hitler used to describe his enemies, but there may have been some question about whether Trump knew he was using the same words Hitler used to justify his murderous and genocidal rule of Nazi Germany.

Now, after backlash that his words echoed Hitler's, however, there is no doubt.

"They said Hitler said that," Trump said Tuesday after he again told the crowd in Iowa that immigrants are "poisoning the blood" of America.

After insisting Hitler used the words "in a much different way," Trump went on to make the "blood" reference again. "It's true. They're destroying the blood of the country, they're destroying the fabric of our country, and we're going to have to get them out."

In other words, Trump's response when criticized for using Hitler's language was to acknowledge the criticism and then to use it again. Whether he is telling the truth about not ever reading "Mein Kampf," there have been multiple reports of Trump privately admiring Hitler.

As president, Trump reportedly complained that America's military leaders were not "totally loyal" to him, telling his chief of staff, retired Marine Corps Gen. John Kelly, "Why can't you be like the German generals?"

As reported in "The Divider: Trump in the White House, 2017-2021" by Peter Baker and Susan Glasser, Kelly responded by pointing out Nazi generals "tried to kill Hitler three times and almost pulled it off."

And as I reported in "Tired of Winning: Donald Trump and the End of the Grand Old Party," Trump boasted to a Republican congressman that German Chancellor Angela Merkel had told him there was "only one" leader in history who had attracted crowds as large as Trump.

"She told me she was amazed at the size of the crowds that came to see me speak," Trump told the Republican congressman. "She said she could never get crowds like that. In fact, she told me that there was only one other political leader who ever got crowds as big as mine."

The Republican congressman, a close ally of Trump's, couldn't tell whether Trump knew that Merkel was referring to Hitler, who, of course, attracted massive crowds throughout his rule of Nazi Germany.

"And I'm thinking," the congressman told me while recounting his interaction with Trump, "you knew who she is talking about, right?"

Back in 1990 -- decades before he got into politics, Trump reportedly acknowledged owning a copy of "Mein Kampf." The admission came in an interview with Vanity Fair shortly after his divorce from his first wife, Ivana. Here's what the magazine reported:

"Last April, perhaps in a surge of Czech nationalism, Ivana Trump told her lawyer Michael Kennedy that from time to time her husband reads a book of Hitler's collected speeches, "My New Order," which he keeps in a cabinet by his bed. Kennedy now guards a copy of "My New Order" in a closet at his office, as if it were a grenade."

Vanity Fair reporter Marie Brenner asked Trump if his cousin had given up a copy of the book to him. She wrote this is how Trump responded:

"Actually, it was my friend Marty Davis from Paramount who gave me a copy of 'Mein Kampf,' and he's a Jew," Trump told Brenner.

Brenner then asked Marty Davis whether he gave Trump a copy of the book.

"I did give him a book about Hitler,' Davis told her. "But it was 'My New Order,' Hitler's speeches, not 'Mein Kampf.' I thought he would find it interesting. I am his friend, but I'm not Jewish."

Brenner then wrote that Trump told her: "If I had these speeches, and I am not saying that I do, I would never read them."

In other words, Trump's denial in Iowa that he had read "Mein Kampf" was not the first time he has denied reading Hitler -- or the first time there was reason for him to issue such a denial.

ABC News Chief Washington Correspondent Jonathan Karl is the author of three books on Donald Trump: "Front Row at the Trump Show," "Betrayal" and "Tired of Winning."