"I've looked at the legal arguments against it, and I will tell you as a Supreme Court litigator, those arguments are not very good," Cruz, who was then gearing up for his 2012 Senate race, said in 2011 on "The Duke Machado Show."
"As much as someone may dislike the policy of birthright citizenship, it's in the U.S. Constitution. And I don't like it when federal judges set aside the Constitution because their policy preferences are different," Cruz said then.
While Trump says that the Constitution already could be read to not grant birthright citizenship, others in the GOP 2016 field are calling for a constitutional amendment to end the practice.
Cruz on Wednesday said he would “absolutely" support changing the policy.
"We should end granting automatic birthright citizenship to the children of those who are here illegally,” Cruz said in an interview on Michael Medved’s radio show. “That has been my position from the very first day of my running for the Senate.”
But in that 2011 interview, Cruz said, "I think it is a mistake for conservatives to be focusing on trying to fight what the Constitution says on birthright citizenship. I think we are far better off focusing on securing the border, because birthright citizenship wouldn't be an issue if we didn't have people coming in illegally."
Correction: This story previously misstated the year Ted Cruz said ending birthright citizenship was a "mistake." He gave the interview in 2011.