The so-called "birthright citizenship" concept some find in the Fourteenth Amendment made sense when it was important to grant citizen rights to freed slaves following the Civil War. It hasn't made sense for some decades.
Yahoo Politics reports the views of GOP presidential nominee aspirants regarding this doctrine. Seven oppose it, listed in alphabetical order: Carson, Graham, Jindal, Paul, Santorum, Trump, and Walker. Seven favor it: Bush, Fiorina, Gilmore, Huckabee, Kasich, Pataki, and Rubio. Not clearly on record, but leaning "anti" are Christie and Cruz.
Needless to say, three of the four Democrats favor the doctrine. Webb's views are not reported. Virtually nobody is taking the candidacies of Republicans Santorum, Gilmore, and Pataki seriously, nor those of Democrats O'Malley and Webb.
Opposing birthright citizenship could become a litmus test for conservatives, one of several. Inasmuch as children born to foreign citizens who are resident in the U.S. are automatically citizens of the same nation as their parents, this doctrine is not needed and should be scrapped.