Here's how the logic works (according to World Net Daily's Joe Kovacs): "While the Constitution does not define 'natural-born citizen,' there is strong evidence that the Founding Fathers understood it to mean someone born of two American citizens."

Kovacs (and he is not alone) goes on to reason that Rubio's "eligibility is in doubt" because - though his parents were legal U.S. residents when he was born - they were not yet naturalized citizens.

Who knows how big this thing will get - maybe it's just a small fringe movement - but it is a "thing."