Ted Cruz responded to John McCain questioning his eligibility for the presidency, saying the Arizona senator is secretly trying to boost Marco Rubio's chances at the Republican nomination.

"I think it is no surprise to anybody that John McCain is going to be supporting Marco Rubio in this election," Cruz told Mark Halperin of Bloomberg's With All Due Respect. "It's no surprise at all that he's trying to do what he can to help the candidate that he's favoring who he thinks shares policy positions with him."

The Texas senator's rebuttal comes hours after McCain said during a Phoenix radio interview that Cruz's birth abroad and his eligibility to become president is "worth looking into."

"I think there is a question," McCain said.

Responding on Friday to Cruz's charge that the Arizona senator was backing Rubio, McCain spokesperson Rachael Dean said, "As Senator McCain has said in the past, he will not be endorsing a primary candidate at this point in the race."

The issue was first raised by Republican front-runner Donald Trump on Monday. “Republicans are going to have to ask themselves the question: ‘Do we want a candidate who could be tied up in court for two years?’ That’d be a big problem,” he told the Washington Post.

Cruz was born in Alberta and lived in Canada until he was 4 years old. He renounced his Canadian citizenship in 2014, and, because he was born to an American mother and father, is an American citizen. 

"The legal question is straightforward and clear," Cruz said.

McCain faced questions about his own eligibility when he ran for president in 2008. As Cruz cited when speaking to press on Wednesday, McCain was born on a military base in the Panama Canal Zone. "That's different from being born on foreign soil," McCain said.

"It's not surprising that political opponents who are worried about our surging support among conservatives are trying to muddy the water and are trying to see if reporters will run down crazy rabbit trails because they want to distract from the simple reality that conservatives are uniting," Cruz said.

But if a judge were to rule that Cruz is not eligible to run due to his birthplace, the Texas senator may not seek to change the rules. When asked about people such as his father and Arnold Schwarzenegger—people who immigrated to the United States and love the country but were not natural born citizens—he would not say if the Constitution should be changed to allow for those who gained citizenship later in life. 

"At the end of the day, we have the Constitution we have, and it has served us very well for over two centuries and we should follow the Constitution," Cruz said.

During the interview, Cruz also said he disagrees with Trump's idea to place a 45 percent tariff on Chinese exports, which the real estate mogul proposed on Thursday during an editorial board meeting with the New York Times. The Texan said that large tariffs historically hurt American jobs, and pushed the alternative of placing a 16 percent business flat tax on imports. 

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