He’s only been in Washington since January, but Sen. Ted Cruz (R-Tex.) is the subject of rampant speculation that he will be a presidential candidate in 2016, particularly after his recent visit to the early-primary state of South Carolina.

But complicating the calculus is that Cruz, 42, was born in Canada, raising questions about whether he is even eligible to seek the presidency.

Cruz spoke at a state Republican fundraiser Friday and was warmly received by top donors and activists as he railed against the Obama administration’s handling of several issues.

As he explores the possibility of running for president, Cruz faces several potential questions, including whether he would be viable in a field already populated by other Republican lawmakers, including Sens. Marco Rubio (R-Fla.) and Rand Paul (R-Ky.) and Rep. Paul Ryan (R-Wis.).

Then there is the question about his birthplace.

The Constitution states the president must be a “natural-born citizen.” Cruz’s mother was a U.S. citizen when he was born (his father was born in Cuba) and current law extends citizenship to anyone born to a U.S. citizen, regardless of where the birth takes place. The question is whether U.S. citizenship is the same thing as being a “natural-born citizen.”

Cruz’s spokesman Catherine Frazier said Monday that the senator “is a U.S. citizen by birth, having been born in Calgary to an American-born mother.”

Cruz would not be the first presidential candidate to face questions of eligibility.

Democrats in 1967 suggested that Republican George Romney would not be eligible to serve as president, because he was born to U.S. citizens in Mexico. But a New York Law Journal piece at the time argued forcefully that he would be eligible, which seemed to put the issue to rest. Ultimately, Romney’s primary campaign imploded based on comments he made about the Vietnam War.

More recently, Sen. John McCain (R-Ariz.), who was born in the Panama Canal Zone to U.S. citizens, faced questions about his eligibility when he earned the GOP nomination in 2008. The Senate passed a resolution stating that McCain was indeed a natural-born citizen after he secured his party’s nomination.

The issue of eligibility dates back to Chester A. Arthur, who began facing questions of his eligibility after becoming president in 1881. Democrats claimed that Arthur, a Republican, wasn’t born in the northern reaches of Vermont as he maintained but in a far southern section of Canada.

The nonpartisan Congressional Research Service has even weighed in on the issue, writing in November 2011 that people born to U.S. citizens in foreign countries “most likely” qualify as natural-born citizens.

“The weight of more recent federal cases, as well as the majority of scholarship on the subject, also indicates that the term ‘natural born citizen’ would most likely include, as well as native born citizens, those born abroad to U.S. citizen-parents, at least one of whom had previously resided in the United States, or those born abroad to one U.S. citizen parent who, prior to the birth, had met the requirements of federal law for physical presence in the country,” wrote CRS’s Jack Maskell.

During his remarks in South Carolina on Friday night, Cruz repeatedly referenced his father, Raul Cruz, recounting that he had fought for the Cuban revolution but was later imprisoned, beaten and nearly killed before fleeing to Texas at the age of 18.

“My dad has been my hero my whole life, but what I find most incredible about his story is how commonplace it is,” Cruz told the crowd. “Every one of us could come up here, one after the other, and tell a story just like that. We are all the children of those who risk everything for freedom. I think that’s the most fundamental DNA of what it means to be an American.”

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