The immigration issue is going to tear America apart, and the truly damaging ripping could begin when the caravan of mostly Central American migrants, currently about 7,000 strong and making its way through Mexico at about 40 miles per day, arrives at the U.S. border in 20 days or so. What happens when they get there is difficult to predict, but it could be ugly. The country’s immigration dilemma will almost surely rise to new levels of political passion and rancor.

More than any other issue in America today, the immigration issue is definitional—hinging upon questions of what kind of country America is and what kind of country it is going to be. Huge numbers of Americans, probably close to half the population, view their government’s mass immigration policies and inability to defend U.S. borders as a threat to America’s old cultural identity, the folkways and mores handed down through generations. Another large population segment, perhaps also close to half, views mass immigration and hospitable borders as an integral part of the country’s humanitarian heritage and a fundamental element of its definition.

Many issues helped propel Donald Trump to the presidency in 2016, including the hollowing out of the country’s industrial base, the economic savaging of its working class, the promiscuous foreign policy initiatives of presidents Bush and Obama, and America’s decline as a global force. But the single most potent propellent was immigration. Trump voters were inclined to believe that the country’s elites—globalists at heart—didn’t really care about borders. They saw the elites as trying to finesse the issue to find a way to grant amnesty to some 11 million illegals already in the country while paying only lip service to the need for stopping the inflow.  

Trump knows that immigration was the single most significant factor in his election. To maintain good standing with his constituency, he must stop that caravan.

But how? According to news reports, more caravans are forming up in Guatemala and other Central American countries, and the fate of the lead group is widely viewed as guidance for the others on how to proceed. As Father Mauro Verzeletti, a mission director in Guatemala City, told The Wall Street Journal, “This is a massive phenomenon. It has no precedent in the history of Central America.”

And it poses a stark dilemma for the American government. Jorge Chabat, an expert on U.S.-Mexican relations at Mexico’s University of Guadalajara, captured the reality of the situation in an interview with the Journal. “There is pressure from Trump to return the migrants,” he said, then asked, “but how do you do that with the thousands that have crossed without having an incident where somebody could get killed?” On the other hand, “if you let them all in, then tomorrow you will have four more caravans.”

liberals like to point out that we’ve seen a nearly 75 percent decline in arrests of illegals at the border since 2000, when some 1.6 million were detained. True. But that still represents nearly 420,000 a year, and some 40 percent of those are unaccompanied children or people traveling as families. That poses a particularly difficult problem because it is almost impossible to stem that tide without family separation and incarceration while asylum claims and law enforcement procedures are adjudicated. But that approach is considered unacceptable by the American people on humanitarian grounds, as reflected in the outcry when the Trump administration sought to employ it as a deterrent.

And it seems clear that stealthy crossings are down in part because those wishing to enter the United States have adopted a new approach—seeking asylum based on professions of persecution in their home countries. The 361-judge immigration court was facing a backlog of 765,000 asylum cases as of September 1, up from just 542,000 at the beginning of the Trump administration.

What this tells us is that the country’s apparatus for handling asylum cases isn’t even remotely adequate to the challenge even in normal times. With 7,000 asylum seekers on their way to the border, and with more caravans likely if they succeed, the U.S. system will break down completely. Trump calls the country’s immigration laws “a disgrace,” and Wall Street Journal columnist Dan Henninger considers that an “indisputably non-false thing” for the president to say.

So what can the president do to stem the tide and forestall future caravans? How can he meet the challenge without increasing tensions on this emotional issue? He has little maneuver room, given the powerful pro-immigration sentiments of elite institutions and the country’s upper crust, which has largely managed to insulate itself from the disruptions that occur in the wake of significant immigration waves (while availing itself of inexpensive household help). Consider just two headlines in two elite newspapers. The New York Times: “Trump Escalates Use of Migration as Election Ploy,” with the sub-headline “Stoking Voters’ Anxiety with Baseless Tale of Ominous Caravan.” And The Washington Post: “For Trump and GOP, a bet on fear, falsehoods.”

These headlines—and many more like them, as well as most of the coverage from the elite media—reflect the reality that many elites simply don’t see a problem here. And anybody who does is violating the norms of political discourse, as established and enforced by the elites. Or at least, the elites sought assiduously to enforce those norms of discourse and largely did—until Trump came along and exposed the profound fault line embedded in the country on this issue.

Senate Minority Leader Chuck Schumer and House Minority Leader Nancy Pelosi manifested a similar blasé attitude toward the caravan in a joint statement they put out as it made its way into Mexico. They accused Republicans of being “desperate” to change the subject from health care to immigration because voters oppose the GOP’s positions on the health issue. So here we have the two top Democrats demonstrating that they are entirely unmindful of the implications of this caravan development—as indeed they and their congressional colleagues seem largely unmindful of the immigration fault line and its capacity for agitating the body politic.

Trump fumed about all this in his inimitable way as he sought—and continues to seek—ways to halt the caravan. He enjoined Mexico and Central American countries to halt the procession, to no avail. He threatened them with aid cutoffs if they didn’t do it, also to no avail. He has ordered military troops to the border, to join National Guard troops already there, in supporting the efforts of border security personnel. It isn’t clear what actual impact that could have. He has threatened to close American ports of entry, which would have a seriously deleterious effect upon U.S. commerce and the economy.

Yet amidst all the president’s fuming and tinkering, the caravan just keeps coming. What happens, we must ask, if some of its people try to simply overrun U.S. border personnel, as they did in entering Mexico from Guatemala? What happens if violence erupts?

The caravan represents a rebuke to any American claim that its borders are inviolable. A large chunk of the U.S. population accepts the rebuke and says we must welcome these people on humanitarian grounds because they are fleeing wretched conditions in their home countries. Another large chunk says absolutely not, because U.S. acceptance of the rebuke would represent a serious erosion of national sovereignty.

Therein lies America’s immigration dilemma. The caravan isn’t just a caravan. It is a threat to the country’s civic comity, or what’s left of it.

Robert W. Merry, longtime Washington, D.C. journalist and publishing executive, is a writer-at-large for The American Conservative. His latest book is President McKinley: Architect of the American Century.