BOULDER, Colorado—GOP presidential candidate and former Pennsylvania Sen. Rick Santorum went after fellow GOP presidential candidate Sen. Lindsey Graham (R-SC) on the issue of increasing legal immigration, arguing that Graham’s position hurts the American worker.

“We have an immigration policy that Senator Graham supported that brings in even more low-wage workers into this country. He says he wants to solve problems. That’s great, but you’re not solving problems for American wage earners,” Santorum challenged. “You’re not solving problems for workers in America, who have seen their wages flatline and have been disaffected enough to leave the workplace.”

Santorum said that America is facing the lowest labor participation rate in 50 years and pointed out that roughly 35 million legal and illegal immigrants have entered the U.S. in the past two decades.

“We have low wages, low participation rates. Maybe there’s something going on, like we don’t have the right match, right? We aren’t giving the training and the investment in our workers, and we’re bringing in people to compete against low-wage workers. That’s what is happening,” he explained. “We need to get better training, better skills, including vocational education and training in community colleges.”

Santorum’s comment toward Graham’s immigration stance came after CNBC’s debate moderator Carl Quintanilla asked Graham, “[You] have said you believe that climate change is real. You said you accept tax increases as part of a budget deal with Democrats. You’ve co-sponsored a Senate immigration bill, providing a path to citizenship for those in the country illegally. Are you in the wrong party’s debate?”

“No, I think I’m trying to solve problems that somebody better solve,” Graham said. “I want to secure the border because, if we don’t, we’re going to get hurt and hit again. I want to fix a broken visa system. I want to increase legal immigration because we’re going to have a shortage of workers over time.”

As to the 11 million, I want to talk about fixing the problem. We’re not going to deport 11 million people and their legal citizen children, but we will deport felons. And those who stay will have to learn our language to stay, because I don’t speak it well, but look how far—how, at the end of the day, folks, I am trying to solve the problem and win an election. I’m tired of losing.

Graham was one of the sponsors of the failed 2013 Gang of Eight legislation with fellow GOP presidential candidate Sen. Marco Rubio (R-FL) that advocated a pathway to citizenship—which many conservatives oppose as amnesty.