OTTUMWA, Iowa–Donald Trump responded Saturday to the fine the United Kingdom’s Environment Agency slapped on him for the pollution from his private jets.

“I flew my plane to a certain location and they sent me a bill for $2,220—a carbon tax. I said, ‘What a scam. What kind of a scam is this?’”

Trump went after President Obama for riding on Air Force 1, which Trump says creates a large carbon footprint, while advocating for climate change policy.

“Think about it, he gets into Air Force 1, which is a very old 747 with the old really big engine and if you’re a believer in the carbon footprint, you don’t like this…He flies a 747 to Hawaii and back and then gets up and gives a speech about global warming.”

The Republican presidential primary frontrunner also took shots at his nearest opponent, Texas Sen. [crscore]Ted Cruz[/crscore], who is ahead of Trump in some polls in the Hawkeye state.

Trump made no mention of Cruz’s releasing his birth certificate and his mother’s birth certificate but doubled down on his allegation that the Texas Republican still had an eligibility issue for the Oval Office.

“I will say CNN has us at 53/51. And Fox has us pretty much tied and we’re doing fine. We’re pretty much tied with Ted Cruz and we’ll talk about that. I like Ted, but he’s got to straighten out his problem. He’s got to straighten it out. He can’t have that problem and be the nominee. He’s got to straighten it out. He’s got to get it taken care of,” Trump said.

Cruz was asked about the issue by an attendee during a Townhall meeting in Mason City.

The law is straightforward on this. Under the Constitution, in order to be president, you must be a natural born citizen. Now, U.S. law has been clear from the very first days of this country that the child of a U.S. citizen born abroad is a natural born citizen. Indeed, the very first Congress, when it passed the first laws on citizenship, defined the child of a U.S. citizen born abroad as a natural born citizen. They used exactly those words. Now mind you, many members of the first Congress were themselves Framers who had been at the constitutional convention who had used the exact same words in the Constitution. This is an issue that has come up many times in American history. For example, many of us know [crscore]John McCain[/crscore] was born in Panama. But he was a U.S. citizen because both of his parents were U.S. citizens. He was a citizen by birth. Likewise, George Romney, Mitt’s dad, who ran for president in ’68, was born in Mexico. His parents were Mormon missionaries, and yet he was a U.S. citizen by birth because his parents were citizens. And the third example, interestingly enough, is Barry Goldwater. Goldwater was born in Arizona before Arizona was a state, it was just a territory. And so he was a U.S. citizen by birth by virtue of the fact that his parents were citizens. And so as a legal matter, the question is quite straightforward. My mother was born in Wilmington, Delaware. She is a citizen by birth, so I became an American citizen by virtue of being born to her. I have never breathed a breath of air on this planet when I was not a U.S. citizen. I’ve never been naturalized. It was the process of being born that made me a U.S. citizen.

Trump also accused Cruz of being in U.S. oil companies pockets’. The New York billionaire reiterated his ability to fund his own campaign and not be bought by outside influences, noting that “even his enemies are offering him money” he says he is turning away.

“I’m so tired of these weak tired disgusting corrupt politicians we have,” he said.

“You think they’re stupid, the politicians, and many of them are, but many of them are just corrupt. They take their PACs. Guys take $5 million, $7 million, $2 million, $1 million into Bush’s PAC, and Hillary’s PAC, and Marco’s PAC. All of these PACs and frankly, Ted Cruz has two guys that are giving him a fortune. One is oil and one is something else,” Trump said, adding a veiled reference to ethanol.

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