Michael Fix, Senior Fellow and former President of Migration Policy Institute, in an Aug. 2015 article, "Repealing Birthright Citizenship: The Unintended Consequences," available at the Migration Policy Institute site, stated:

“The reality is this: Repealing birthright citizenship would create a self-perpetuating class that would be excluded from social membership for generations. Working with researchers at Pennsylvania State University, the Migration Policy Institute (MPI) has found that ending birthright citizenship for U.S. babies with two unauthorized immigrant parents would increase the existing unauthorized population by 4.7 million people by 2050. Crucially, 1 million would be the children of two parents who themselves had been born in the United States. Under a scenario denying U.S. citizenship to babies with one parent who is unauthorized, our analysis finds that the unauthorized population would balloon to 24 million in 2050 from the 11 million today.

This last finding alone should give pause. Touted by its supporters as a solution to reduce illegal immigration, repeal in fact would have the completely opposite effect.

More crucially, the idea that the U.S.-born children, grandchildren, great-grandchildren, etc. of people born in the United States would themselves inherit their forefathers’ lack of legal status would have deep implications for social cohesion and the strength of the democracy itself. This perpetuation of hereditary disadvantage based on the legal status of one’s ancestors would be unprecedented in U.S. immigration law…

So why would we alter a hard-fought, 147-year-old constitutional principle that addressed one of the darkest chapters in our history and has served the country so well? We should not: there is nothing about eliminating birthright citizenship that is in the national interest.”

Aug. 2015