Cruz's citizenship again questioned during Republican debate

After a week of trading barbs about Sen. Ted Cruz's citizenship, he and Donald Trump brought the fight to the debate.

Cruz was born in Canada to an American mother. He maintains his citizenship is "settled law."

At Thursday's debate, Donald Trump said, "I was born here. Big difference."

To which Cruz replied, "On the issue of citizenship, I'm not going to use your mother's birth against you."

"Because it wouldn't work," Trump quipped.

Trump has been bringing up Cruz's citizenship as an issue for some time.

"There's a big question mark on your head, and you can't do it to the party," Trump said.

"I'll tell you, I'm not going to be taking legal advice from Donald Trump," Cruz said.

This video includes images from Getty Images.