US News & World Report

By Nicole Hemmer

For all the talk about populism and personality, the GOP nomination battle now underway pivots on a single issue: immigration.

Sure, the general election will go much broader. The eventual nominee will focus on Planned Parenthood, religious freedom, taxation and the size of government. But in the primary, these issues have been sidelined. After all, the remaining 16 candidates are of one mind on issues like abortion and lower taxes. Not so with immigration. And in the intraparty battle over immigration policy, it is the pro-reform candidates who have been on the losing side.

Signs of the immigration debate's divisiveness appeared in 2005–06, when President George W. Bush attempted to advance immigration reform. Grassroots opponents quickly pushed back, clashing with pro-immigration activists in ugly battles that undermined the "compassionate conservative" approach so central to Bush's domestic policy agenda.

In 2012, immigration served as an under-the-radar litmus test. As frontrunner in the GOP contest, Rick Perry argued that conservatives who didn't support educational funding for undocumented children didn't "have a heart." The backlash was intense. Perry, who until then had topped the polls, plummeted, never to recover.

Some commentators have pointed to his "48-second brain-freeze" on the debate stage in 2012 as the defining moment of Perry's presidential ambitions. But it was immigration, not immobilization, that sunk his 2012 hopes. His "oops" moment was merely the nail in the coffin of a candidacy that had already met its demise. Mitt Romney understood as much, latching on to a policy of "self-deportation" in an effort to sidestep the thickets Perry so blithely wandered into.

Perry's 2016 experience only serves to underline this point. Over the past four years, the former Texas governor worked hard to improve not only his image but his skills. On the campaign trail he was nuanced, forceful and completely unable to rouse the interests of voters and donors.

There have been other warning signs as well. Marco Rubio and Jeb Bush, both widely perceived as frontrunners in the GOP race, have floundered in the immigration debate. When Rubio backed comprehensive immigration reform in 2013, he instantly earned a RINO designation. He went from an early front-runner to a back-of-the-packer. It took until April 2015 for his numbers to begin to recover — helped, no doubt, by his studied avoidance of immigration policy. Likewise, Jeb Bush's declaration that border-crossing represented an "act of love" not only brought derision but ensured he would never win the hearts of the Republican base. As a result, both candidates have struggled in the 2016 primaries.

Further underlining the tendentiousness of immigration is Donald Trump. Catapulting to the front of the pack after calling Mexican border-crossers, murderers and rapists, Trump has been joined by Ben Carson. Both have well-burnished anti-establishment credentials — neither man has ever held elected office — but it is telling that both are firmly on the right when it comes to immigration. Though Carson has criticized Trump's rhetoric (and Trump's off-the-cuff plan to deport 11 million undocumented workers), he also opposes birthright citizenship, prefers guest worker status to immigration, and has been a vocal opponent of sanctuary cities.

Immigration has become a defining issue in Republican politics, as it has for politicians in Europe, Britain and Australia. It touches on a number of central issues: nationalism, economics, culture, national security. Because of this, much more is at stake in this struggle over immigration policy than the soul of the Republican Party. Immigration policy is not just about who Republicans are, but who we are as Americans. Despite all the efforts to make the GOP more inclusive, the 2016 race is showing that for Republicans, America is not a land of opportunity, but of exclusion.

This article was originally published in the US News & World Report