The GOP debate crowd in North Charleston, S.C., repeatedly booed Donald Trump on Thursday night as he again questioned Sen. Ted Cruz’s eligibility for the presidency.

“If you become the nominee, who the hell knows if you can even serve in the office?” Trump said, renewing his allegations that Cruz is not a “natural-born citizen” under the Constitution because he was born in Canada.

Cruz dismissed the argument, saying it’s “straightforward” that he counts as natural born under current immigration law. Cruz blamed his former law professor, Lawrence Tribe — whom he described as a “left-wing judicial activist Harvard law professor” — for stirring up the controversy about his eligibility. The Supreme Court has never ruled on the issue of whether a person born outside the country to a U.S. parent counts as a “natural-born citizen.”

Cruz also suggested that Trump, who last September dismissed the issue of his eligibility, was motivated to attack him because of his rising poll numbers.

“Since September, the Constitution hasn’t changed, but the poll numbers have,” Cruz said.

The two got into a heated back-and-forth, with Cruz saying that Trump’s mother was born in Scotland, which under one definition of “natural-born” might exclude him from eligibility.



“I’m not going to use your mom’s birth against you,” Cruz said. Trump shot back: “Because it wouldn’t work.”



“You have great constitutional lawyers who say he can’t run,” Trump insisted. “I’m not bringing a suit, I promise, but the Democrats are going to bring a lawsuit.”

Cruz suggested wryly that if Trump’s theory is correct and he’s ineligible, it could benefit the real estate mogul.

“If this all works out, I’m happy to consider naming you as vice president, and if you happen to be right, you can get the top job at the end of the day,” the Texas senator joked.