Heritage Foundation President Jim DeMint, the former senator from South Carolina, is defending the conservative think tank’s research into the fiscal effects of an immigration overhaul.

Earlier this month, supporters of the Senate bill pre-emptively attacked Heritage Senior Research Fellow Robert Rector for what they contend was a “flawed” a 2007 study examining the cost of providing a path to citizenship for millions of illegal immigrants. The Cato Institute and Grover Norquist of Americans for Tax Reform have charged that Rector’s latest study on the subject, which has yet to be released, will probably be similarly flawed and does not represent conservatives.

Heritage opposes an immigration overhaul and DeMint, in a lengthy blog post published Monday, criticized the path to citizenship component of the Senate immigration bill written by the “gang of eight.” In the post, DeMint devoted a paragraph to defending Rector and the Heritage Foundation’s research.

“The Heritage Foundation is one of the only organizations looking at this cost to taxpayers. Our expert, Robert Rector, is one of the nation’s leading authorities on government social programs, and he is currently calculating what amnesty will cost taxpayers over the long term. It is based on a methodology also used by the National Academy of Sciences,” he wrote.

Rector’s previous study examining the cost of legalizing the millions of illegal residents is blamed by pro-reform forces for helping dissuade Republicans from supporting the failed 2007 effort to rewrite U.S. immigration law.