Sen. Marco Rubio, R-Fla., has been at the top of many prognosticators’ lists as the man to be a vice presidential candidate on the 2012 GOP ticket. But he’s insisting it won’t be him, despite a flub that had him citing his performance “as vice president.”

At an event hosted by National Journal, he said he wouldn’t take the position even if Mitt Romney, the leading candidate for the GOP nod for president, says he needs him.

He slipped a minute later, saying, “If in four to five years, if I do a good job as vice president – I’m sorry, as a senator. … If I do a good job as a senator, instead of a vice president, I’ll have a chance to do all sorts of things.”

The first-term senator has been cited repeatedly as a potential GOP vice presidential candidate, even though a document found in the National Archives raises questions about whether he actually is qualified constitutionally to serve as president or vice president.

The Petition for Naturalization on behalf of Mario Rubio, the senator’s Cuban father, has been retrieved from the National Archives and posted online by the PixelPatriot website, confirming that Marco Rubio was about four years old when his parents became U.S. citizens. Specifically, Mario Rubio was naturalized as an American citizen in 1975, based on the Sept. 9, 1975, date on the petition; Marco Rubio was born in 1971.

So why would all this matter insofar as the senator’s eligibility to serve as vice president? The question is whether Rubio is a “natural born citizen” – constitutionally required of all presidents – a unique citizenship status defined by the Founding Fathers, according to many legal experts, as being the offspring of two citizens of the country.

Of course, the same question has dogged Barack Obama since before the 2008 election and continues to this day. While Obama claims to have been born in Hawaii, the birth document he released with great fanfare at the White House in April 2011 has been determined by multiple document experts as well as a six-month law enforcement investigation almost certainly to be a forgery.

Yet even if Obama could document a Hawaii birth, he still arguably would not qualify as a “natural born citizen” of the United States since he was not born of two U.S. citizen parents, Obama’s father having been a Kenyan national.

Compounding all the controversy over presidential eligibility is the fact that the Constitution does not define “natural born citizen,” requiring legal and historical research to determine precisely what the Founders meant.

Attorney Herb Titus, who has taught constitutional law for nearly 30 years and was the founding dean of the College of Law and Government at Regent University in Virginia Beach, Va., says the “natural born” language was used because the Founding Fathers wanted a leader without divided loyalties.

“That’s precisely what a natural-born citizen is,” Titus said in a YouTube video, “one who is born to a father and a mother, each of whom is a citizen of the United States or whatever other country they’re claiming natural-born citizenship in.”

His explanation:

The Los Angeles Times reported that Rubio has rejected suggestions he is a VP candidate twice in just recent days.

“Marco has said repeatedly that he’s not going to be vice president, and all the speculation in the world isn’t going to change that fact,” Todd Harris, a senior Rubio adviser, said in the LA Times.

“I don’t’ want to be the vice president,” Rubio told Major Garrett of the National Journal.

“So, if Mitt Romney asks, you will say no?” Garrett asked.

“Yes. But you know he’s not going to ask. That doesn’t work. He’s watching this interview right now,” Rubio responded.

Some of the earliest concerns over the loyalties of the commander-in-chief were raised in a 1787 letter from John Jay to George Washington.

Wrote Jay, who later became president of the Continental Congress and the first U.S. Supreme Court chief justice: “Permit me to hint, whether it would be wise and seasonable to provide a strong check to the admission of Foreigners into the administration of our national Government; and to declare expressly that the Commander in Chief of the American army shall not be given to nor devolve on, any but a natural born Citizen.”

In fact, Congress in 1790 defined “natural born citizen” as a child born of two American citizens, but the law containing the definition was repealed several years later.

“The Law of Nations,” a 1758 work by Swiss legal philosopher Emmerich de Vattel, was read by many of the American founders and informed their understanding of law later established in the Constitution.

Vattel specified that a natural-born citizen is born of two citizens and made it clear that the father’s citizenship was a loyalty issue.

Explains Vattel: “The natives, or natural-born citizens, are those born in the country, of parents who are citizens. As the society cannot exist and perpetuate itself otherwise than by the children of the citizens, those children naturally follow the condition of their fathers, and succeed to all their rights. … In order to be of the country, it is necessary that a person be born of a father who is a citizen; for, if he is born there of a foreigner, it will be only the place of his birth, and not his country.”

Also, in 2008, when the U.S. Senate resolved that Sen. John McCain, R-Ariz., the Republican presidential nominee, was a natural born citizen, it specified that his parents were American citizens at the time of his birth.

The non-binding resolution, co-sponsored by then-Sen. Barack Obama, stated that McCain – born to two American citizens on an American military base in the Panama Canal Zone in 1936, “is a ‘natural born citizen’ under Article II, Section 1, of the Constitution of the United States.”

The Article II Superpac posted an analysis arguing that the parents of a “natural born citizen” must be citizens at the time of his or her birth. The organization noted that Supreme Court rulings suggest the term applies only to those born on U.S. soil to citizen parents.

Joseph Farah, founder and CEO of WND.com, also has argued that the definition of “natural born citizen” excludes Rubio.

“Rubio is, quite simply, not a ‘natural born citizen’ by the accepted legal, English-language standard as it has been known throughout American history. He was born in Florida to two non-U.S. citizen parents,” he wrote.

“I know this is not a popular notion among Republicans, just as it wasn’t among Democrats when challenges were made to Obama. However, the Constitution should always trump political expediency.

“This is not a ‘technicality,’ as some might suggest. If we don’t adhere to the Constitution on matters as significant as presidential eligibility, then the Constitution ceases to be a meaningful document for guiding our nation. Indeed, it becomes the kind of ‘living document’ that many liberals have claimed it should be – ever-changing to new circumstances,” he said.

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