In an interview with Univision, Leahy strongly criticized the study, which said that a bipartisan Senate immigration reform bill would cost $6.3 trillion over the next few decades. Leahy also called out Jason Richwine, one of the authors of the study, who wrote a Harvard thesis that argued they have low IQs, partially due to genetics.

"I do not agree with the study," Leahy said. "I think the study is bogus. It goes against everything we’ve seen. One of the people who wrote that study now, it’s turned out, has made some, what I consider some demeaning and racist comments about Hispanics. I just think it’s absolutely wrong."

On Friday Richwine resigned from his post at Heritage. After The Washington Post first reported on Richwine's thesis, more reporting revealed that he made similar arguments during a speech at the American Enterprise Institute in 2008. In that speech, Richwine said there are "real differences" between white Americans and non-white immigrants, "and they're not going to go away tomorrow."

"I think those statements are absolutely wrong. I think they’re racist. And they certainly don’t reflect the Latinos I know," Leahy said. "They don’t reflect the people I’ve known in the community. And come on, I mean I can hear them saying this about my grandparents as they were learning English. Oh, they don’t have communicative abilities. Or my wife, her first language was French because her parents were from French-speaking Canada. Obviously, she speaks both French and English perfectly. You know, this is racism and — one good thing — almost every senator I’ve talked with in both parties reject this kind of reasoning."