We need to get clear: birthright citizenship was a core principle at the founding of the Republic in 1776. Yet now, Senator Lindsey Graham of South Carolina wants to hold Senate hearings on the bedrock constitutional precept that "All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States."
There is considerable confusion about birthright citizenship. The nativists and those pandering to them with talk about "real Americans" and border invasions by "Muslim Mexicans" (there's an oxymoron for you, and I use the latter two syllables advisedly) know that the language above is from the 14th Amendment, passed in 1868 to guarantee citizenship to four million ex-slaves in the still rebellious Confederate States of America. Senator Graham suggests that by now it has served its purpose, and is encouraging a flood of "illegals," who are ruining our social fabric.
Bad history and noxious politics tend to go together. We inherited birthright from England, as part of common law, and it was universally recognized at the republic's Founding. Every young lawyer in America, from James Madison to Abraham Lincoln, prepped for the bar by reading William Blackstone's Commentaries on the Law of England, which declared:
The first and most obvious division of the people is into aliens and natural-born subjects. Natural-born subjects are such as are born within the dominions of the crown of England, that is, within the ligeance, or as it is generally called, the allegiance of the king; and aliens, such as are born out of it.
American legal scholars, lawyers, and politicians simply adapted the English law of birthright subjectship to the terms of republican citizenship. Eminent jurists like Chancellor James Kent, often called "the American Blackstone," put it clearly in his Commentaries on American Law:
Citizens, under our Constitution and laws, mean free inhabitants, born within the United States, or naturalized under the laws of Congress. If a slave born in the United States be manumitted, or otherwise lawfully discharged from bondage, or if a black man be born within the United States and born free, he becomes thenceforward a citizen...
By the time Kent wrote these words (1841) a fierce battle had ensued over whether birthright applied to all Americans, even those "of color." Kent, along with a wide range of Northerners, was quite sure it did. Conversely, a certain kind of white person, by this time identified with Andrew Jackson's "Democracy," asserted that whiteness was a test of Americanism. They pointed to decisions made by Congress in the 1790s, restricting membership in the federal militia and access to naturalization by immigrants to white people.
There were valid arguments on both sides, but generally the race-blind believers in birthright made a better case: that ten of the thirteen original states allowed free black men to vote; that Americans of African descent had been recognized as citizens by the federal government in various ways (even Andrew Jackson had hailed his free black soldiers as "fellow citizens" after the Battle of New Orleans). No one ever denied that individual states could and did make black men citizens, with full voting and civil rights, the question was whether that made them citizens of the United States. So when Chief Justice Roger Taney finally attempted to settle the matter, with his infamous opinion in Dred Scott v. Sandford in 1857 that black people never had been and never could be American citizens, no matter how long they had been here, respectable opinion across the North was profoundly shocked. Here Lincoln is representative: he had never been an abolitionist, and was uncertain about what he thought of black people, but he knew very well that they had been and could be American citizens. Dred Scott went a long way toward radicalizing men like Lincoln, firming their resolve as Republicans to choke off slavery and guarantee a nation "by the people, of the people, for the people," meaning the whole people.
The point of all this history is plain: when you hear that birthright citizenship is some latter-day concept, not part of the America conceived by the Founding Fathers, take a strong drink of skepticism. It is core to who we are, and the last time it was challenged, a bloody civil war ensued. We need to protect it, as we would protect the nation itself.