You’d think comprehensive immigration reform legislation would be a done deal. President Barack Obama has promised to overhaul immigration policy since his 2008 campaign, and leading Republicans have been keen to do the same in the wake of the last presidential election. Two weeks ago, the U.S. Chamber of Commerce and the AFL-CIO, representing the interests of Corporate America and organized labor, respectively, endorsed a series of reform proposals, including a substantial increase in work visas and labor-friendly prevailing wage requirements. A bipartisan group of eight senators has been working toward a deal, and a bipartisan group of eight House members is also in on the act. So what’s the holdup?

The basic problem is beautifully illustrated by two little controversies, one sparked by liberals and the other by conservatives. On the left, there is a widely held belief that U.S. immigration laws are far too stringent, and that we’re not doing enough to help low-income immigrants become citizens. On the right, there is an equally common conviction that U.S. immigration laws should not, as a general rule, have the effect of expanding the number of people who depend on means-tested government benefits to maintain a decent standard of living.m

In a recent New York Times op-ed piece, Rahm Emanuel, the blustery mayor of Chicago and Obama’s former chief of staff, and Luis V. Gutierrez, an Illinois congressman who represents a large share of Chicago’s Latino population, argue that, in order to apply for citizenship, Citizenship and Immigration Services is charging immigrants too steep a price – $680, including a fee for fingerprinting. Emanuel and Gutierrez observe that as the fee has increased over the past decade the number of lawful permanent residents who apply for citizenship has declined. They neglect the possibility that other factors could be at play.

As Princeton University sociologist Douglas Massey and former Mexican Foreign Minister Jorge G. Castaneda have observed, an average of 29,000 Mexican-born immigrants become citizens each year in the decade before 1996, a number that has surged to 125,000 per year since then. Even if there has been a dip in naturalizations in recent years, the number is still higher than it had been in the years before 1996, when the fees were lower. The chief driver of this post-1996 increase in naturalization rates, according to Massey and Castaneda, is that as Mexican-born immigrants perceived that the political environment was growing more hostile to non-citizens, they chose to react defensively. Specifically, Congress passed legislation in 1996 limiting access to a number of federal benefits to citizens, a signal that immigrants who had been quite content to remain non-citizens ought to naturalize if they wanted to be full members of the American community.

Perhaps a changing political climate has reassured immigrants that they needn’t naturalize to enjoy the benefits of living in the United States. The Obama administration is committed, for example, to extending subsidized health insurance coverage to lawful permanent residents under the Affordable Care Act. And lawful permanent residents who have resided in the United States for five years or more are already eligible for Medicaid, a program that is set to expand dramatically in the years to come. The post-1996 wave of “defensive naturalization” has created a large and growing political constituency that is keen to defend the interests of foreign-born non-citizens, which is in part why the political momentum behind comprehensive immigration reform has been growing.

Another way of looking at the decline in naturalization rates is that families are weighing the costs and benefits of citizenship and deciding that it’s not worth the trouble. That is, if the $680 fee that Emanuel and Gutierrez write about is too steep a price to pay for naturalization, naturalization is not actually worth $680 to them, possibly because lawful permanent residents have access to many if not most of the federal, state and local benefits, including subsidized health insurance coverage, that are available to citizens. Citizenship confers the right to participate in the U.S. political process, and of course this right is very important to some. But it’s not quite as important to others. Rather than cut the $680 fee, Emanuel and Gutierrez could achieve their stated goal of increasing the naturalization rate by calling for trimming benefits for non-citizens. But doing so would anger the immigrant voters who were part of the post-1996 “defensive naturalization” wave, and so it is a non-starter for Democrats.

Conservatives are less concerned about courting a backlash from immigrant voters and more concerned about dependency. As Byron York recently reported, in August 2012 a group of four Republican senators – Jeff Sessions of Alabama, Orrin Hatch of Utah, Charles Grassley of Iowa, and Pat Roberts of Kansas – wrote a letter to the Department of Homeland Security expressing their dismay about the criteria used to evaluate applicants for legal permanent residence in the U.S. While American consular officers are allowed to consider whether immigration applicants are likely to be eligible for Supplemental Security Income or Temporary Assistance for Needy Families, they are not allowed to consider whether the applicant in question might make use of Medicaid, food stamps and various other means-tested benefits. This is despite the fact that, as York explains, federal law explicitly states that any immigration applicant who “is likely at any time to become a public charge is inadmissible.” Granted, the definition of who is and is not a “public charge” will vary. But among conservatives, at least, including the large number who believe there is a place for a limited safety net, the idea that we ought to admit immigrants who are likely to prove economically self-reliant over those who are not makes intuitive sense.

While it might seem extremely difficult to reconcile the views of Emanuel and Gutierrez, who want to make it as easy as possible for immigrants earning very low incomes to become citizens, and Sessions and his allies, who want to make it much harder for aspiring immigrants who are likely to earn very low incomes to settle in the U.S. in the first place, there is one idea that might appeal to both sides of the debate.

In his highly underrated 2010 book, From Immigrants to Americans, Jacob Vigdor, a Duke University economist, proposes an “assimilation bond.” To make his proposal concrete, Vigdor sets the price of the bond at $10,000, but the number could be much lower or higher. The idea is that immigrants would pay a fee of $10,000 to enter the country, yet they would receive substantial reimbursement for meeting various assimilation milestones. Completing an accredited English-language course, for example, would yield a refund of $2,000. Immigrants who speak fluent English on arrival would receive a commensurate discount. Naturalization would also yield a rebate of $2,000. And every year, immigrants who paid the fee would receive a credit against federal income taxes of up to $500 until only $500 is left. Immigrants who work steadily, learn English and naturalize will have paid back almost all of the bond after 11 years.

Vigdor’s proposal elegantly addresses a number of conservative concerns, as it creates a powerful incentive for immigrants to work steadily at jobs that generate at least some income tax liability. It also raises the stakes for immigrants, who will have to make a significant up-front financial commitment to living and working in the U.S. Emanuel and Gutierrez would presumably object to the fact that an expensive assimilation bond would prove a barrier to many low-income immigrants. With this in mind, Vigdor suggests that churches and foundations could sponsor immigrants who lack the necessary funds, and the same could be true of relatives and perhaps even friends and employers. Suffice it to say, an American who has to spend $10,000 to sponsor an immigrant will be far more discerning than one who has to do little more than fill out paperwork and wait. More important, from the perspective of immigration advocates, the Vigdor proposal rids the immigration system of enormous amounts of red tape. Left and right can duke it out over whether the price of the assimilation bond should be set at $10,000 or $20,000 or $5,000. But the basic idea has tremendous potential.