Birtherism -- the belief that Barack Obama was born in Kenya, not in the United States -- pretty much died last year when the White House released a copy of the president's long-form birth certificate showing he was born in Honolulu on Aug. 4, 1961. After that, the number of Americans who doubted Obama's place of birth dropped dramatically.
But not to zero. In recent days, there has been a mini-resurgence of birther talk, from Arizona, where the secretary of state questioned Obama's eligibility to be on the ballot, to Iowa, where some Republicans want to require presidential candidates to prove their eligibility for office.
The talk has gone beyond Obama, with some buzz on the Internet suggesting that Florida Sen. Marco Rubio, a leading Republican vice presidential contender, is not a natural-born American citizen.
The two cases are different. Birthers questioned whether Obama was, in fact, born in the United States, while they claim Rubio, indisputably born in Miami, is not eligible because his parents were not citizens at the time of his birth.
The one thing that characterizes both arguments is an ignorance of the law concerning citizenship.
The Constitution specifies that a president must be a "natural born citizen" of the United States, but it does not define the term. The Supreme Court has never clarified the issue, but there is a law, 8 U.S. Code 1401, that spells out in detail who is a citizen.
The law uses the phrase "citizens of the United States at birth" and lists categories of people who fit that description.
First, there are people born inside the United States. No question about that; their citizenship is established by the 14th Amendment.
Then there are the people who are born outside the United States to parents who are both American citizens, provided one of them has lived in the U.S. for any period of time. And then there are the people who are born outside the United States to one parent who is a U.S. citizen and the other who is an alien, provided the citizen parent lived in the United States or its possessions for at least five years, at least two of them after age 14.
Since they are all "citizens of the United States at birth," the question is, does that also mean they are "natural born citizens" in the constitutional sense?