Donald Trump said people can immigrate to the U.S., but only if they do so legally.
"If we need people, they have to come into this country legally. It's fine. If they come in they have to come in legally," he said during Wednesday's Republican debate.
Sen. Marco Rubio said the legal immigration system should be scrutinized as well.
"Our legal immigration system from now on has to be merit-based," he said. To be considered, an immigrant must show skills and a willingness to be an American, Rubio added.
Rubio himself is the son of immigrants from Cuba.