May 10 (Bloomberg) -- Immigration reform is dividing conservative groups in Washington. The Heritage Foundation has produced a report saying reform with a path to citizenship will cost taxpayers more than $6 trillion. The report has been widely criticized for bad methodology -- and some of the loudest critics have been other right-of-center groups, like Grover Norquist’s Americans for Tax Reform.

Partly, this reflects old divisions in the Republican Party: Business interests want more immigrants for a deeper labor pool and more economic growth, while conservative base voters tend to be skeptical of immigration. But it also reflects growing distance between establishment conservatives and Heritage, a think tank which acts increasingly like a Tea Party pressure group with a policy research arm.

Heritage fought hard to block Speaker John Boehner’s so-called Plan B for resolving the fiscal cliff in December – ensuring that Republicans would be seen as having no alternative to Barack Obama’s plan. They have egged on congressional Republicans into debt limit fights that cooler conservative heads would rather avoid. And last month they managed to kill a proposal from Majority Leader Eric Cantor to modestly expand high-risk insurance pools for people with pre-existing conditions, depriving Republicans of a health-care talking point beyond “repeal Obamacare.”

Heritage has become a roadblock to Republicans advancing good policy and winning political fights. It has become a voice for a faction of conservatives who would rather be ideologically pure than advance a viable agenda or win a majority of the electorate. It’s basically doing from outside Congress what its president, former Senator Jim DeMint, used to do from inside. And as I wrote back in December, other Republicans didn’t appreciate DeMint’s antics in the Senate and weren’t likely to be big on them when he became head of a think tank, either.

So it’s no surprise that many conservatives in Washington are glad to take the group down a peg. Immigration has given them that chance; unlike fiscal issues, immigration enables them to take Heritage to the woodshed without looking like squishes.

A lot of liberals are almost gleeful over the infighting. (If you doubt this, run a Twitter search on “Heritage” and “popcorn.”) But if this fight actually ends up reducing the influence of the Heritage Foundation over Republican policymakers in Washington, it will have strengthened conservatives politically, making them a less bumbling foe to liberals.

(Josh Barro is lead writer for the Ticker. Follow him on Twitter.)