01/15/2016 09:55 EST | Updated 01/14/2017 05:12 EST

Ted Cruz Defends Canadian Birth During Republican Presidential Debate

"I'm not going to be taking legal advice from Donald Trump."

WASHINGTON — It was Calgary's big moment on the American political stage Thursday — as a candidate defended his right to run for president of the United States despite being born in the biggest city of Alberta.

Sen. Ted Cruz responded with indignation as he was pressed on his Canadian birth, by both the moderators of the Republican debate and by his emerging nemesis Donald Trump.

"I've spent my entire life defending the Constitution before the U.S. Supreme Court," said Cruz, who is running neck-and-neck with the real-estate mogul in Iowa. 

"And I tell you, I'm not going to be taking legal advice from Donald Trump."

Sen. Ted Cruz speaks during the Fox Business Network Republican presidential debate. (Photo: Chuck Burton/AP)

The partisan crowd appeared to back him up, cheering the Texas senator and booing when the debate moderator and Trump dabbled in the country-of-birth issue.

Trump fired back that multiple constitutional scholars have raised Cruz's birth as a legal question mark. One of them is Harvard's Laurence Tribe — who happens to be Cruz's former law professor.

"Take it from your professor," Trump retorted. He urged Cruz to go get a judge's opinion certifying his right to run, lest he later become the nominee and find his candidacy tied up in court: "There's a big question mark over the head. And you can't do that to the party."

Cruz points out that Tribe is a Democrat. And he pointed out that his increasingly bitter rival only started raising the issue as his poll numbers improved in Iowa.

Cruz's critics have revelled in the fact that he was born in Canada to an American mother and Cuban-American father, and spent his first few years there as they worked in the Alberta oil industry.

"I'm not going to be taking legal advice from Donald Trump."

Some pranksters have attempted to edit his Wikipedia page to point out his Canadian birth. A lawsuit has already been launched, and more are expected.

Several constitutional scholars have emerged to call it a legitimate question because they say the Supreme Court has never ruled on the definition of what constitutes a "natural-born" U.S. citizen, which is a constitutional requirement to run for president.

Tribe says he believes Cruz should qualify — only because Tribe personally favours a flexible approach to interpreting the Constitution, one that evolves over the centuries.

But he noted an irony: Cruz himself sees the Constitution differently.

Cruz a constitutional 'originalist'

He's a strict originalist who believes the Constitution should be interpreted exactly as written — which means, according to this view, that the 18th century right to bear arms for the purposes of a militia should extend to all 21st-century U.S. citizens and include new forms of high-powered weaponry.

"To his kind of judge, Cruz ironically wouldn't be eligible," Tribe wrote in the Boston Globe. 

"Because the legal principles that prevailed in the 1780s and '90s required that someone actually be born on U.S. soil to be a 'natural born' citizen."

Cruz pointed out that his former professor was a committed Democrat. Trump replied that several other scholars have voiced similar concerns.

Cruz recently relinquished his Canadian citizenship, which he was granted at birth.

Also on HuffPost

Photo gallery Sen. Ted Cruz See Gallery