Rookie Senator Ted Cruz, Republican from Texas, has already endeared himself to the GOP's Tea Party base.

In the process, he has garnered national headlines for a stance that is often as critical of Democrats as it is of his own party.

And though he's barely getting started in his first shot at national politics, he's already mulling a potential presidential run in 2016. 

Only that he may not actually qualify to be president of the United States. The constitution stipulates that only a "natural-born citizen" is eligible to hold the highest office in the country -- and given that Cruz was born in Canada, it's unknown if he'd qualify for U.S. president.

He's not the first whose citizenship has been called into question.

The so-called "birther" issue dogged both President Barack Obama, whose critics claimed was born in Kenya though he’s long insisted he was born in Hawaii, and former presidential candidate John McCain, an Arizona GOP senator who was born in a U.S. Naval base in Panama.

But Cruz’s case has a bit of a different twist. 

The senator was born in Calgary, Canada, to a Cuban immigrant father and an American mother, in 1970. His father did not become an American citizen until 2005. The assumption is that Cruz was an American all along through his mother.

Children born abroad to American parents have what's legally called "derivative" U.S. citizenship.

Cruz spent the first four years of his life in Canada before his family moved to Houston, Texas, where he was raised.

So is he then a "natural-born" citizen? 

In 2008, then Illinois Sen.Ba rack Obama embarked on his initial run for the presidency and was attacked by the “birther” movement, which declared that the senator was ineligible because he was allegedly born in Kenya, demanding to see his birth certificate. Obama released his birth certificate showing he was born Honolulu, simmering down the attention on the issue – although some continue to question the validity of the document.

But while President Obama’s citizenship was dredged up based on conspiracy theories and his travel as a child, other candidates have also had to address the issue because of where they were actually born.

Obama’s 2008 opponent John McCain was declared ineligible by the same movement because he was born on U.S. soil in Panama, a charge which McCain summarily dismissed.

Cruz is also quick to dismiss such criticism.

He addressed the issue with Sean Hannity on his Fox News show in March, brushing off presidential aspirations at the time but clarifying to the host that he is an American through and through.

“My mom was a U.S. citizen, so I'm a citizen by birth,” Cruz told Hannity.

Fox News senior judicial analyst and former New Jersey Superior Court Judge Andrew Napolitano believes Cruz is eligible as well.

"The children of at least one American citizen are natural-born citizens, no matter where they were born," Napolitano said.

Not so fast, some say -- starting with the very leaders of the "birther" movement that continue arguing President Obama is not an American.

“He is not eligible,” Orly Taitz, a lawyer and dentist from California who started the movement, told Fox News Latino. “It’s not personal. I really like him.”

Taitz said he would advise Cruz not to waste money on an explorative committee and instead demand a ruling from the courts on the issue. 

Fox News Latino contacted Cruz’s office, but repeated messages seeking comment were not returned.

The Constitution states that only “a natural born citizen, or a citizen of the United States, at the time of the adoption of this Constitution” is eligible to run for president.

Many have long interpreted the wording as to mean that only those who are born in the United States can hold the nation’s highest political office.

But experts claim the issue is more nuanced than it seems.

Larry Sabato, a national political expert who directs the Center for Politics at the University of Virginia, said considering its volatile nature, the issue should not be left in limbo. The Supreme Court should make a final and definitive call, he noted.

“There has to be some kind of way to get a ruling on this,” Sabato said. “We need one now.”

Such a step is necessary because the Founding Fathers did not make it clear exactly what they meant by "natural-born citizen." Thus the myriad interpretations floating around.

The upshot is that Cruz should not necessarily thinks he's a shoe-in. His team may ultimately prevail, but he may face quite a hard time getting there.

"They’re going to have to assemble a packet of statements of widely prominent constitutional lawyers that say he is eligible to run,” Sabato said.

Cruz is not the only potential Republican presidential candidate being dogged by the birther issue. Florida Republican Sen. Marco Rubio, who has drawn the ire of some GOP  leaders because he supports a bipartisan immigration reform effort, has already faced questions about whether he’s a “natural-born citizen.”

When Rubio was being talked about as a possible running mate for former presidential candidate Mitt Romney, “birthers” argued that because the senator’s parents were both born in Cuba, the Miami-born politician was not a “natural born citizen.”

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