Throughout the Bush and Obama administrations, the outlines of a grand bargain seemed relatively clear. The left would get its amnesty, to help shield millions of foreign-born workers from exploitation at the hands of unscrupulous employers, though it would be euphemistically rebranded as a path to earned legalization, in deference to those with bitter memories of periodic amnesties that had come before. Meanwhile, the libertarian right, closely aligned with many of the very same unscrupulous employers frowned on by the left, would get a vast expansion of guest-worker visas and stringent limits on safety benefits of legalized migrants. As for restrictionists, they’d get the promise that once the new immigration system was up and running, illegal entries would be greatly reduced, thanks in large part to a strengthening of workplace enforcement. Because the vast majority of unauthorized migrants come to the U.S. in search of more remunerative employment, effective workplace enforcement has long been seen as the sine qua non of immigration control.

Yet without exception, restrictionists opposed this grand bargain, which in its Gang of Eight iteration would have greatly increased legal immigration levels. To them, the grand bargain was no bargain at all; rather, it was an attempt to marginalize their concerns that a sweeping amnesty would stimulate further unauthorized migration and that a superabundance of low-skill labor would exacerbate many of the country’s existing economic and social challenges. Partisans of the Obama-era grand bargain tended to see restrictionist opposition solely as a manifestation of ethnic chauvinism. This is despite the fact that, as the political scientists Morris Levy and Matthew Wright have observed, a substantial portion of the opposition to an amnesty is driven by a commitment to the rule of law. While amnesty advocates tend to see the issue in attribute-based terms—they want to grant unauthorized migrants legal status on the basis of their individual characteristics, such as their work ethic and their overall ability to make a positive contribution to the country—amnesty opponents are more inclined to make categorical judgments, in which individual merits aren’t really the issue: You could be a deeply admirable person, but you still broke the law, and you shouldn’t be rewarded for having done so. Levy and Wright find that as many as one-third of Americans reject the idea of an amnesty for unauthorized migrants on these grounds, without regard for ethnicity or class.

In short, the problem with the Obama-era grand bargain is that it got the correlation of forces wrong. Though libertarian conservatives are well-represented among elite Republicans, most of whom were, until recently, favorably disposed toward high immigration levels, their views were very much at odds with rank-and-file conservatives, and with older populist voters who had begun shifting their allegiances from an increasingly socially liberal Democratic Party to the GOP. Donald Trump recognized this cleavage within the Republican Party, and he leveraged it to secure its 2016 presidential nomination. So it is hardly surprising that he has endeavored to live up to his promises to the party’s restrictionist base by, among other things, committing ICE to arresting and deporting long-resident unauthorized migrants. Why should he change course now?