Correction: An earlier version of this article incorrectly said that a Heritage immigration study Jason Richwine co-authored found that low-skilled immigrants have lower IQs than the average American. The study found that such immigrants have less education, as the article said, but it not address IQ. This version has been corrected.

The co-author of a disputed immigration study by the Heritage Foundation, a conservative think tank, resigned Friday after questions were raised about racially charged conclusions made in his previous work.

The departure of Jason Richwine, who joined the organization in 2010, came as Heritage sought to move past a barrage of criticism from liberals and conservatives alike over the methodology used in its report that pegged the cost of legalizing 11 million undocumented immigrants at $6.3 trillion.

Heritage spent months preparing for its rollout of the report, which it hoped would reset the immigration debate in Washington and provide a splashy introduction for its new president, Jim DeMint, a former Republican senator from South Carolina.

Instead, the report has landed with a thud this week, placing the venerable institution under fire even from longtime allies on the right. The fall from grace came less than five weeks after DeMint took the helm in a surprise move after leaving Congress.

“What’s so disappointing about the Heritage immigration study is that it is so different from their other work,” said Alex Nowrasteh, a policy analyst at the Cato Institute, a libertarian think tank. “They employed a statistical method that no other economist would use to measure things like this, and on such an important policy issue. And they predictably reached terrible results.”

Heritage officials declined to comment on Richwine’s departure. But the self-inflicted wound has reverberated inside Washington’s influence industry and, according to several people familiar with Heritage, has set off a round of internal recriminations.

For DeMint, the missteps have set up a tricky choice over whether to stand by the immigration report or back away from it, considering that the negative publicity has blunted any potential policy impact.

So far, the organization has defended its methodology, which determined that low-skilled immigrants have less education and will earn less money and need more benefits than average Americans.

The report recommended that lawmakers allow high-skilled immigrants into the country but stem the flow of lower-skilled workers.

Many fellow conservatives argued that Heritage failed to account for potential economic growth once undocumented immigrants are granted citizenship. The study also comes at a time when the Republican Party is trying to broaden its appeal among Hispanics and Asians.

The Heritage study loomed large within conservative circles even before it was published. Participants in weekly conference calls held by a coalition of conservative groups that support immigration talked often about their fears that Heritage could have a major impact on the debate, according to one person involved in the conversations.

A similar Heritage study, published in 2007, helped sink a comprehensive immigration reform bill in the Senate by asserting that the plan would cost $2.7 trillion, alarming Republican lawmakers.

In April, the Cato Institute and another group, Americans for Tax Reform, circulated letters on Capitol Hill warning members of the potential flaws in the Heritage study’s research methods.

“Unfortunately, this study inaccurately reflects only one side of the ledger,” Grover Norquist, the president of Americans for Tax Reform, told Congress’s Joint Economic Committee this week.

The study’s lead author, Robert Rector, told people during briefings that he was modeling the 2013 study on the one from 2007.

Richwine wrote in his doctoral dissertation at Harvard University in 2009 that there are deep-seated and likely genetic IQ differences between the races and that low-IQ immigrants should be kept out of the country.

Heritage sought to distance itself from those opinions. But critics noted that the think tank’s report argued forcefully for keeping less-educated immigrants out of the country.

Sen. Marco Rubio (R-Fla.), a tea party favorite who helped develop the immigration bill and denounced the Heritage study, noted that his own parents, who emigrated from Cuba, did not graduate from high school. “I would not say they were a burden on the United States,” Rubio said. “My parents were a lot better off 25 years after they emigrated here than they were when they first got here.”

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