Yes, Ted Cruz is a natural-born citizen

Under the law in effect when Cruz was born in 1970 (i.e., statutes applying to people born between 1952 and 1986), the requirement was that, at the time of birth, the American citizen parent had to have resided in the U.S. for ten years, including five years after the age of fourteen. Cruz’s mother, Eleanor, easily met that requirement: she was in her mid-thirties when Ted was born and had spent most of her life in the U.S., including graduating from Rice University with a math degree that led to employment in Houston as a computer programmer at Shell Oil…

So The Donald needn’t fear. Like President Obama, President Cruz would spend more time working on which turkeys to pardon on Thanksgiving than on frivolous legal challenges to his eligibility. Ted Cruz is a natural born U.S. citizen in accordance with (a) the original understanding of that term, (b) the first Congress’s more demanding standard that took both parents into account, and (c) the more lax statutory standard that actually applied when he was born, under which birthright citizenship is derived from a single American-citizen parent.