Donald Trump speaks at a town hall in Des Moines, Iowa, on Friday. (Photo by Steve Pope/Getty Images)

DES MOINES, Ia. -- Donald Trump is done holding back his insults for Sen. Ted Cruz (R-Tex.).

During a rally here on Friday night, Trump repeatedly slammed Cruz for not supporting continued subsidies for ethanol, a major business in Iowa, and suggested that Cruz took this stand because of his ties to major oil companies based in Texas. Trump also made a vague reference to Cuba, the home country of Cruz's father, and tied it to evangelical voters, who play a major role in the Iowa caucuses. Bob Vander Plaats, president of the Family Leader, an influential conservative Christian group, recently endorsed Cruz.

"We're doing really well with the evangelicals," Trump said. "And, by the way: And again, I do like Ted Cruz -- but not a lot of evangelicals come out of Cuba, in all fairness. It's true. Not a lot come out. But I like him nevertheless. But I think we're going to do great, and we are doing great with evangelicals."

Cruz's campaign has yet to comment on Trump's attacks.

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For months, Cruz and Trump maintained a rather friendly relationship on the campaign trail, defending one another and abstaining from attacks. But now that Cruz is gaining ground in Iowa, he has become a threat to Trump. Within minutes of taking the stage on Friday night, Trump mentioned Cruz and called him "a nice guy," a label he repeated several times throughout the night.

"Everything I say, he agrees with me -- no matter what I say," Trump said. "But with the ethanol, really, he's gonna come a long way because he's right now for the oil. But I understand because big oil pays him a lot of money. He's got to be oil, right? The oil companies give him a lot of money."

Trump quickly pivoted to reminding the audience that he does not have a super PAC official supporting his candidacy. He described super PACs as "no good," "terrible" and "corrupt."

"I'm with you. I'm with everybody. I'm with everybody," Trump said. "Look, I'm self-funding. I have no oil company. I have no special interest. I have no lobbyists."

The rally was held in a large exhibition hall on the state fair grounds, which was far too large for the roughly 1,500 people who attended. Trump's campaign surrounded the stage with ethanol proponents wearing green T-shirts and other local conservative activists who were allowed to ask the candidate questions. One person asked Trump if Cruz's ethanol position is "because of his ties with big oil"?

"Yes, it is," Trump said. "It is. Well look, he's from Texas -- to the best of my knowledge, there's a lot of oil in Texas, right? So, you know, he gets a lot of money from the oil companies, and he's totally against ethanol."

Trump reflected on the the major impact ethanol has had on Iowa, including "tremendous numbers of jobs."

"I say to myself: If Ted Cruz is against ethanol, how does he win in Iowa?" Trump said. "Because that's very anti-Iowa."

Another person asked Trump what role Cruz would play if Trump becomes the nominee: "Will you name him your vice president... or appoint him to the United State Supreme Court?" The crowd applauded the question.

"I like Ted Cruz a lot," Trump said. "He's doing well, I'm doing well. I mean, it's not a contest between the two of us, just so you understand... But I do like him, and I would say that we would certainly have things in mind for Ted."

Katie Zezima contributed to this report from Washington.