Billionaire businessman Donald Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE on Saturday unleashed a personal attack at Wisconsin Gov. Scott Walker, days after being the target of the governor’s latest campaign blast.

Trump’s speech in Iowa came on the heels of a fundraiser for Walker referring to the New York business mogul as “DumbDumb” in an event invitation email earlier this week.

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Blasting the “horrible” insult from Walker’s campaign, Trump went on the offensive with criticism against Walker’s economic record.

“Wisconsin is in turmoil,” Trump told a boisterous crowd at a rally in Iowa. He pointed to the state’s roads, schools and hospitals, which he said were all “a disaster.”

Walker, who is leading polls in Iowa, remains one of Trump’s biggest rivals in the race.

“I hear the only person beating me in Iowa is Scott Walker,” he said. “I can’t believe I’m in second place. Folks, will you please put me in first place so I feel better?”

Trump told the crowd Saturday that he had helped Walker win his race because he admired the candidate’s “fight,” but didn’t know what he was fighting for. “I’ve been very nice to him,” he said.

But after Walker’s fundraising email went public, Trump declared: “I can finally attack.”

In response to the controversy, Trump fundraiser Gregory Slayton told the Wall Street Journal, “I didn’t mean that to be public but obviously I stand behind it.”

He added: “Look, this is a great country. Guys who are not that smart can get rich, it’s wonderful. But Donald Trump is not going to be president of the United States ever, period, end of story.”

Walker leads the GOP 2016 field in Iowa, according to a RealClearPolitics average of polls, with 18.8 percent support.

Trump sits in third with 8.5 percent, tied with Sen. Rand Paul (R-Ky.) and right behind Florida Gov. Jeb Bush, who has 9 percent support.

Trump also took aim at Jeb Bush — and the rest of the GOP presidential field — for dependence on campaign benefactors.

“A guy like Bush, a guy like Walker, are controlled by the people who give them money,” Trump said. “They will be bombarded by their lobbyists who donated a lot.”

Trump again tried to use his wealth and blunt style to separate himself from the rest of the Republican field.

“The other guys running, the Republicans — they protect each other," Trump said early in his speech. “Me, I don't care.”

Trump’s speech in Oskaloosa, Iowa, comes a week after his last high-profile appearance in the early-voting state, when he questioned the war hero status of Sen. John McCain (R-Ariz.), who had been captured as a prisoner of war.

His comments prompted a firestorm among congressional Republicans, who have lined up behind McCain. Still, Trump’s popularity has surged in the Republican field.

Since then, his campaign has rushed to prove it has support from veterans. A former member of the U.S. Navy Seals helped warm up the crowd Saturday, proclaiming that "Donald Trump loves veterans, unlike some others who think we're 'crazies,' " referring to a comment by McCain about Trump supporters.

During his speech, Trump pulled out hundreds of pages of letters from veterans that he said represented just one day’s worth of mail.

“Nobody fights harder for veterans than me,” Trump asserted, pointing to his role in building the Vietnam memorial in New York City.

He also slammed the embattled Department of Veterans Affairs as ”the most corrupt group of people in all of Washington.”

Trump also continued damage control for remarks he made about “Mexican rapists” earlier this month, which prompted a trip to the border city of Laredo, Texas, this week.

“It’s really, really dangerous,” Trump said about his trip, suggesting the experience had changed the minds of people, even reporters, who previously said his remarks had been “a horrible thing.”

“Now I have people calling me up — I have journalists calling me up — saying I was right,” he said. He said the reporters were "petrified, thought they were going to get killed."

Trump has had a tumultuous week with the media. One day earlier, his staff revoked access to his event to the Des Moines Register after its editors penned a critical editorial.

During his speech, he blasted the newspaper as a “super liberal rag” that he said is “not respected around here,” prompting applause.

A reporter for the state’s largest newspaper tweeted Saturday that she and another reporter were covering the event. She noted that Trump’s staff were “polite” and the candidate was “silent” when they made eye contact.

Trump entered the auditorium to "You’re the Best Around" by Joe Esposito, best known as the “Karate Kid” theme song. After the hour-long speech, he left the stage to “We're Not Gonna Take It" by Twisted Sister — a favorite on his campaign trips.