Leading conservative think tanks are entering a pitched battle over the fiscal costs, or benefits, of immigration reform. But while right-wing support for an immigration bill may help its chances of passing, many immigrant advocates worry that fiscal conservative backing comes with troubling strings attached. Most notably, they fear that because of pressure from the right, immigration reform will exclude newly legalized immigrants from Obamacare.

In 2007, leading right-wing think tank The Heritage Foundation released a report that claimed the reform bill in the works that year would cost taxpayers trillions. Now, according to news reports, The Heritage Foundation’s Robert Rector plans to release a new version of that report and anti-immigration groups hope it will again dampen reform’s chances.

But the arguments are met by pro-reform counter attacks from other, equally high profile conservatives, including anti-tax demagogue Grover Norquist and the libertarian Cato Institute. A email this morning to Republican lawmakers from Norquist’s Americans for Tax Reform reportedly warns against Rector’s analysis.

"Robert Rector’s work does not speak for the conservative movement," the letter reads.

The Cato Institute, which has often supported more open immigration policy, released a paper last week attacking Rector’s 2007 analysis. "That 2007 report’s flawed methodology produced a grossly exaggerated cost to federal taxpayers of legalizing unauthorized immigrants," writes Cato’s Alex Nowrasteh.

A white paper released today the American Action Forum, a conservative group, claims that immigration reform could reduce the federal deficit by $2.5 trillion over the next decade.

For many immigration reform advocates, the conservative support is a mixed bag. While they recognize a bill can only pass with bipartisan support, the conservative influence also makes it likely that deficit fears will outweigh the needs of low income immigrants.

"While we understand that cost is a significant issue with any piece of legislation, we think that if Congress is going to spend millions of dollars on a border that is already secure, that that money would be better spent fully integrating immigrants into American society by providing them with access to health coverage," says Don Lyster, Washington director for the National Immigrant Law Center, which advocates for low-income immigrants.

All signs from Washington suggest that immigrants who gain provisional status will be excluded from the healthcare exchanges set up under Obamacare. The White House draft immigration bill leaked earlier this year would exclude new immigrants from healthcare exchanges and the Obama has also excluded Deferred Action recipients from accessing ACA exchanges.

Now, Politico reports that a bill drafted by a group of House members may exclude newly legalized immigrants from access to Obamacare for 10 years while they wait to apply for a green card. And several sources familiar with the beltway deliberations say that the Senate bill will likely do the same.

Lyster and others say immigrants would be left for a decade or more with few options but to go to the emergency room or buy expensive private insurance outside of the exchanges, a financial impossibility for most immigrants.