Trump Questions Canadian-Born Cruz's Eligibility for President

U.S. Republican presidential candidate Ted Cruz speaks with the media at a campaign stop at Danny's Sports Spot in Cherokee, Iowa, on Tuesday. The stop is a part of Cruz's six-day bus tour through Iowa. REUTERS/Mark Kauzlarich

With less than a month before Iowans caucus, Republican front-runner Donald Trump is going negative against his closest competitor in the state, U.S. Senator Ted Cruz of Texas.

In an interview with The Washington Post on Tuesday, Trump said Cruz's birthplace—Canada—could be a "precarious" issue for the Republican Party. Trump didn't go so far as to say that Cruz's birthplace was disqualifying. Rather, he insinuated that, were Cruz to win the GOP nomination, he could face a yearslong legal battle to prove his eligibility.

In order to become president, the Constitution stipulates that, besides having to be at least 35 years old and a resident of the U.S. for 14 years, a candidate must be a "natural born citizen." While the Constitution does not make explicit what a "natural born citizen" is, most experts agree the term means a person born with U.S. citizenship—regardless of his or her birthplace.

"While some constitutional issues are truly difficult, with framing-era sources either nonexistent or contradictory, here, the relevant materials clearly indicate that a 'natural born Citizen' means a citizen from birth with no need to go through naturalization proceedings," according to Neal Katyal, a former solicitor general under President Barack Obama and Paul Clement, who held the same position under President George W. Bush.

Even so, the courts have yet to weigh in on the issue, leaving room for doubts—doubts Trump has raised repeatedly in the past few days. "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," Trump told the Post. "It'd be a very precarious one for Republicans because he'd be running and the courts may take a long time to make decision. You don't want to be running and have that kind of thing over your head."

On MSNBC's "Morning Joe" on Wednesday, Trump skirted attacking Cruz directly, instead arguing "a legal mind on the conservative side," whom he declined to name, "has been saying that he has concern that Ted Cruz may not be qualified to be president of the United States."

Were Cruz to become his party's nominee, he wouldn't be the first person born outside the United States to run for president. In 1964, Barry Goldwater, who was born in the U.S. territory of Arizona before it became a state, won the Republican nomination but lost to Lyndon B. Johnson by the largest margin in history at the time. Four years later, Mitt Romney's father, George Romney, who was born in Mexico, ran for the Republican nomination, but lost to Richard Nixon. John McCain, who ran against Barack Obama in 2008, was born in the Panama Canal Zone, a U.S. territory but not a state. At the time, the Senate, which included Barack Obama and Hillary Clinton, passed a resolution intended to settle the issue. "John Sidney McCain, III, is a 'natural born Citizen' under Article II, Section 1, of the Constitution of the United States," it read. The resolution passed unanimously.