Ongoing public disputes between Donald Trump and Ted Cruz have exposed a potential new fault line in the party’s debate over immigration reform: What should the country do about thousands of foreign-born workers that enter the U.S. each year legally to work on temporary visas, ostensibly because domestic or U.S.-born workers are unavailable in sufficient numbers to perform the same jobs? Many of these workers do return home once their contracts expire, but others are recruited to stay permanently, eventually becoming U.S. citizens. Are they displacing American workers and also depressing wages and exposing foreign workers to abuse?  

At the heart of the debate are two little-known visa programs known as H-1B and H-2B that together bring in hundreds of thousands of workers to the United States annually. The H-1B program allots visas to high-skill technology workers and engineers from countries like China, Indian and Korea who are allowed to work for U.S. businesses that can attest that they have tried to recruit domestic or U.S.-born workers to fill the same positions, but could not find qualified candidates. What makes the program so controversial is that U.S. businesses don’t actually make much effort to find domestic workers, reports show, which has led to angry protests from U.S.-trained scientists and engineers. Even worse, a lot of these supposedly temporary workers end up getting green cards, so the program has turned into a “back-door” immigration scheme.

H2-B is similar to H-1B in one key respect: in both programs, the workers are brought in on strictly temporary contracts, with no implied residency rights. However, while H-1B applies to skilled workers, H-2B is designated for unskilled workers only, and the terms of their contracts are far more restrictive. Many of the workers are employed seasonally, in the shrimp industry and tourism, for example. H-2B workers are supposed to leave at the end of their contracts, and most do, but some, it appears, do not. Moreover, because their employment is restricted to a single employer and they have no labor bargaining rights, they are subject to abuse, as numerous independent reports have documented.

Conservatives don’t generally talk publicly about these “guest worker” programs – including the controversial H-2A agricultural visa program — preferring to concentrate their ire on illegal immigration. But behind the scenes there is a fierce debate between business conservatives who like programs that guarantee them access to cheap labor and populist conservatives who genuinely want to see workers, especially American workers protected. The numbers of foreign workers “imported” through these programs, especially H-1B and H2-B, has escalated sharply over the past decade, as businesses in both high- and low-skill sectors continue to push for expanded use of them. For example, H-1B is supposed to be limited to just 85,000 workers annually, but the “cap” is so permeable that businesses often import three times that number, without any effective oversight. And their impact on the status domestic labor is of growing concern.

Various government reports have documented how major American IT companies with operations in countries like India have off-shored thousands of jobs under H-1B, paying workers a fraction of what they once paid their American-born workers. Since American-born workers are generally unwilling to move to India, companies can say they tried to recruit American workers — but couldn’t find any. Adding insult to injury, American-born workers are frequently required to train their own foreign-born replacements, hastening their own departure from the workforce.

Cruz and Trump have all but tripped over themselves trying to explain their respective positions on H-1B and H-2B. Trump says he supports the programs but that they hurt minorities and that he would likely revisit them to ensure that “abuses” were ended. Cruz originally supported a robust expansion of H-1B but has been accused of trying to “parrot” Trump’s populism on the issue in an attempt to vie for base voters.

It’s Trump, however, that actually faces charges of using the H-1B program to exploit foreign workers. He was sued earlier this month by a fashion model who says she was promised a $75,000 a year job on her H-1B visa but ended up making less than one-sixth of that.  Trump, it turns out, has brought in 1,100 foreign workers on guest visas, of whom 250 were fashion models. The problem? H-1B visas are intended principally for individuals who possess “highly specialized knowledge” that is unavailable in the domestic work force but fashion models are included if they possess “distinguished merit and ability.”

It’s the kind of recruiting loophole that rankles H-1B critics.

Guest worker programs like H-1B and H-2B are important to debate sooner rather than later. Assuming that expanded border and interior enforcement works, and the pool of illegal immigrant labor begins to dry up the continuing demand for foreign-born workers will require expanded legal channels of some kind. Business conservatives are certain to argue for expanded use of the guest-worker programs, even allowing some undocumented workers who might otherwise be deported a temporary haven to work, but without guaranteeing them residency or citizenship rights.  

But that kind of proposal will not sit well with populist conservatives who want to see contract labor systems reformed and who fear that allowing illegal aliens to stay will make it more likely that they will eventually be granted residency and citizenship rights. Republicans need to unify on these issues if they expect to pass an immigration reform plan that’s a constructive GOP alternative to “amnesty.”