Surely, it was just a coincidence, but as soon as Ted "Canuck" Cruz crept past GOP national front-runner Donald Trump in Iowa polling a couple of weeks ago, Trump started nudging the issue of Cruz's alleged Canadian-ness. People, Trump said, were talking to him. They had lots of questions about Cruz's potential eligibility to be president. Trump said Cruz was a good guy and probably eligible, but the Texas Senator should seek out a definitive legal opinion before any potential lawsuit got tied up in the courts for years.

Cruz is probably good. The most accepted definition of "natural-born citizen" — something the U.S. Constitution requires any potential president to be — is non-naturalized citizen. Because Cruz, who was born in Canada, is the child of an American mother, he was a United States citizen at birth — not a naturalized citizen.

Still, the ambiguity of the constitutional requirement and the lack of a concrete challenge to a presidential candidacy — plus the additional issue of who would have standing to challenge constitutional eligibility — mean the issue is not completely dead. As Cruz, Trump and the rest of the GOP careen toward another debate on Thursday and then the Iowa caucuses, let's take a look at seven more presidents or presidential aspirants who faced questions about their "natural birth."

1. Chester Arthur — Elected James Garfield's vice president in 1880, Chester Arthur was a New York state machine politician who was dogged throughout his career by accusations that he wasn't born in the United States. Initially, Arthur P. Hinman, a New York lawyer and Democratic operative, floated the idea that Arthur was born in Ireland and emigrated to the United States when he was 14. That theory was quickly discredited by evidence that Arthur's family had, in fact, moved to Vermont before he was born. A more credible birther story, that Arthur's mother was taking a trip to Canada when he was born, would later emerge. Hinman published his findings in How a Subject of the British Empire Became President of the United States near the end of Arthur's presidency — he'd ascended to the big seat after Garfield was assassinated in 1881 — but no official action was taken.

2. Franklin Roosevelt Jr. — Franklin Roosevelt Jr. was long considered a potential candidate to follow in his father's footsteps and run for president. Like Cruz, Roosevelt was born in Canada. He never ran for president, but was elected to the House of Representatives. He served from 1949-1955.

3. Barry Goldwater — Arizona Senator Barry Goldwater secured the Republican nomination for president in 1964. He was born in Phoenix in 1909, before Arizona became a state on February 14, 1912. Because Goldwater was born in a United States territory, there was never any serious pushback to his eligibility to become president, but the whole issue became moot when he was whomped by incumbent Lyndon Johnson in the 1964 general election.

4. George Romney — George Romney, former Michigan governor and Mitt's dad, was born in 1907 to parents who were members of a Mormon colony in Mexico. Because both of his parents were American citizens — they'd been born in the Utah territory — George Romney was a citizen of the United States at birth. His run for the president in 1968 never gained enough traction to make any potential legal challenge worthwhile.

5. Lowell Weicker — Lowell Weicker, a former senator from Connecticut, provides the most directly analogous example to Cruz. He ran for president in 1980, despite being born in Paris to American parents. During his run, his campaign insisted that legal advice they'd received assured them that Weicker would be eligible to serve if elected, just as Cruz's campaign has done. Like George Romney before him, though, he never got close to being elected. 6. John McCain — Another Arizona senator, another birther sorta-mess. Like Goldwater, John McCain was born to American parents in a United States territory — the Panama Canal zone in McCain's case. Unlike Goldwater, McCain actually faced a couple of legal challenges as to his "natural-born" status, but they were thrown out for a lack of standing on the part of the individuals who filed them. 7. Barack Obama — The mother of all birther conspiracies, of course, is tied to Obama. Obama was born in Hawaii to a Kansas-born mother and a Kenya-born father, but conspiracy theorists have long suggested that his birth certificates — he released a short-form birth certificate in 2007 and a long-form birth certificate in 2011 — were forgeries and that the president was actually born in Kenya. Even if that were true, and it isn't, that would put Obama in the same boat as Cruz. Both would've been born abroad to one American parent and one foreign national.

