Birthright citizenship, however, is in the U.S. Constitution's 14th Amendment — specifically, the Citizenship Clause, which states, "All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside."

The 14th Amendment, ratified in 1868 after the Civil War, also states, "No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty or property, without due process of law, nor deny to any person within its jurisdiction the equal protection of the laws."

Speaking to supporters in Eagle Pass, DeSantis also promised to finish the U.S./Mexico border wall that was started under Trump and vowed to help state and local governments enforce immigration laws.

The Florida governor told supporters, "When we go in, on Day 1, we're gonna marshal every bit of authority that we have, will work with Congress when we need to. We'll take executive action when we can, and it will be a Day 1 priority…. I think the states have a role to play. I can tell you, as a president, we are fully going to deputize all state and local governments to be able to enforce immigration law. You will be able to have that authority.”

DeSantis' proposal to end birthright citizenship has inspired a lot of comments on Twitter — some of them highly critical.

The Atlantic's Ronald Brownstein noted that the late conservative Sen. Bob Dole (R-KS) "publicly repudiated that idea" when he ran for president in 1996. And Washington Post columnist Greg Sargent tweeted that birthright citizenship was "one of the crowning achievements of the Republican Party," as historian Eric Foner has noted.

Immigration attorney Curtis Morrison tweeted, "I talk to individuals in the middle east and Africa where babies are born stateless in countries without birthright citizenship (like Saudi Arabia). I find it frustrating that anyone sees babies being born stateless and thinks that's something we need to import here."