It no longer gets much attention, but for several years, Donald Trump's most notable contribution to the political discourse was his "birther" conspiracy theory about President Obama. The New York Republican pushed the racially charged nonsense for quite a while, though it hasn't played a role in his 2016 presidential campaign.
Instead, Trump has shifted his attention to others' eligibility.
Last month, for example, the GOP frontrunner decided to raise questions about Ted Cruz, who was born on Canadian soil to an American mother. Trump has made occasional threats about a lawsuit, though nothing has come of this yet.
On Saturday, the day of the South Carolina primary, Trump went a little further on Twitter, re-tweeting a message that questions Marco Rubio's eligibility, too. On ABC's "This Week," George Stephanopoulos asked the candidate if he really believes his top two rivals are ineligible for the White House.
TRUMP: I'm not really that familiar with Marco's circumstances -- STEPHANOPOULOS: But then why retweet it? TRUMP: Because I'm not sure. I mean, let people make their own determination. I know Ted is being now -- I think he's being sued by somebody having nothing to do with me, by the way. Is being sued by somebody. Maybe it's in New York, having to do with eligibility -- STEPHANOPOULOS: You're really not sure that Marco Rubio is eligible to run for president? You're really not sure? TRUMP: I don't know. I really -- I've never looked at it, George. I honestly have never looked at it.
This is how nonsense starts, isn't it? Trump plants a seed of racially charged doubt, and then he hopes it sprouts.
But in this case, let's nip it in the bud. I can think of all kinds of reasons to be concerned about a Rubio presidency, but his eligibility isn't among them. He's a natural-born citizen. Full stop.
As for why would Trump have any doubts about Rubio's status, note that under Trump's approach to constitutional law, those born on American soil aren't necessarily American citizens.