Since last week’s midterm elections, Donald Trump has spoken less frequently about the migrant caravan, but the subject is still plainly on his mind. On Friday, he signed a Presidential proclamation (“Addressing Mass Migration Through the Southern Border of the United States”), which suspended the possibility of asylum for anyone entering the country between officially designated ports of entry. By U.S. and international law, migrants are allowed to seek asylum “whether or not” they do so at an official checkpoint along the border; Trump’s measure, which was immediately challenged by advocacy groups, including the American Civil Liberties Union, aims to override explicit provisions of an existing federal statute in order to thwart the entry of tens of thousands of Central American migrants. As Lee Gelernt, the A.C.L.U.’s lead litigator in the case, told me, “It would mean the President could literally sit down with a copy of the immigration act that Congress wrote and cross out any provision he didn’t like.”

The night before the President issued his proclamation, members of the caravan gathered in Mexico City, where they’d paused for a week of rest, to vote on a final destination for the group. Of the big border cities in northern Mexico, Tijuana was considered the safest—the route skirts territory controlled by violent cartels—but it was also the farthest away. The caravan now consists of nearly five thousand people, about a third of whom are under the age of eighteen. An estimated three hundred of them are younger than five. Because of the punishing physical toll of the trip, the group has tried, with mixed success, to arrange van and truck transportation the rest of the way. Hundreds of them have either turned back or have been deported by Mexican authorities, while some twenty-six hundred others, according to the Mexican government, have received temporary legal status to remain in Mexico.

The relative success of the group, coupled with the continued desperation of residents in El Salvador, Honduras, and Guatemala, has prompted a string of smaller caravans, consisting of several hundred people each, to travel in its wake. In recent years, under pressure from President Barack Obama, Mexico has redoubled its efforts to intercept Central Americans heading north, earning its own reputation for aggressive immigration enforcement. At the same time, the U.S. has invested about seven hundred million dollars in an aid package, called the Alliance for Prosperity, to try to address the corruption and rampant crime that are seen as the root causes of emigration from the region. “The caravans are not the problem,” Tonatiuh Guillén López, the incoming head of Mexico’s National Migration Institute, said this week. “The issue is the movements we do not see, those who are not in the caravan, that is the big issue.”

For months, the Trump Administration, which has repeatedly threatened to cut foreign aid to Central America as a form of political punishment, has tried to negotiate a special arrangement with the Mexican government. Known as a “safe third country agreement,” it would, among other things, allow the U.S. to automatically send Central American asylum seekers who travel through Mexico back over the border to pursue their immigration cases there. A similar pact exists between the U.S. and Canada, premised on the idea that immigrants have a fair shot at pursuing asylum in the American system. Anyone travelling through the U.S. who arrives at an official Canadian checkpoint to request asylum is turned over to the U.S. Department of Homeland Security. The White House has promised to rescind its asylum ban if Mexico signs a similar deal with the U.S. But, for logistical and humanitarian reasons, this is a non-starter for the Mexicans.

Although migration to the U.S. is still significantly lower than it was two decades ago, the number of people applying for asylum is on the rise, and hard-liners in the Trump Administration claim, in the face of conflicting evidence, that families are gaming the system by entering the country to pursue asylum and then disappearing before their immigration cases come before a judge. “This enrages the Miller cabal,” a former Trump Administration official told me, referring to the President’s senior adviser Stephen Miller. “Miller knows there’s only so much the U.S. can do without changing or limiting those who can claim asylum.” For the past several months, in open violation of international law, Customs and Border Protection has been turning away asylum seekers at official ports of entry, from San Diego to McAllen, Texas, claiming that migrants would have to wait in Mexico until there was enough space to process them. Meanwhile, the President’s proclamation last week lacked any commitment to increase resources at ports of entry to deal with the heightened traffic, and earlier this week C.B.P. issued a warning that there would be further delays. In effect, while the Administration claimed to only be targeting those who enter the U.S. illegally, it was, in multiple ways, trying to shut down the southern border for everyone. Another former Trump Administration official told me, “They really don’t have any more tools beyond just tightening the screws: separate families, eliminate asylum and due process, turn back people at the border.”

On Monday afternoon, a group of seventy-seven Hondurans who’d been travelling with the caravan for the past month arrived in Tijuana, ahead of the larger group. Cesar Mejía, a twenty-three-year-old from San Pedro Sula, with a chin-strap beard and blond highlights in his close-cropped hair, had become, by accident, a de facto leader of a group of L.G.B.T.Q. migrants who formed their own unit within the caravan. When Mejía crossed into Guatemala, in mid-October, he displayed a gay-pride flag that he had stashed in his backpack. “I just left a country where I was discriminated against,” he told me. “I used to get attacked, and I’d go to the police to lodge complaints, but nothing ever happened. When I took out the flag on the caravan, people asked me what country it was from, and I told them, ‘It’s the flag of the world.’ ” In Mexico City, a representative from the advocacy organization RAICES offered to help connect Mejía and other L.G.B.T.Q. travellers with lawyers as they neared the border. U.S. detention facilities can be dangerous, particularly for queer and transgender migrants, and a network of American advocacy groups are now on the ground in Tijuana in anticipation of the caravan’s arrival.

“Trump scared us,” Mejía told me. “But we got to Tijuana, and it wasn’t like what Trump said on TV.” The border was limpia, he told me—by which he meant, free of American troops. As part of a dramatic, preëlection gambit, the President sent fifty-six hundred soldiers to south Texas, hundreds of miles from where the caravan was headed. Since then, the soldiers had very little to do other than set up a patchwork of wire fencing along the border.

Even if the route to Tijuana is comparatively safe—and the border with San Diego clear of infantry soldiers—the city itself poses a number of dangers for migrants trying to enter the U.S. “There are over a thousand asylum seekers waiting at the port of entry right now,” Nicole Ramos, the director of the Border Rights Project at Al Otro Lado, an immigrant-advocacy group, told me on Monday. “When the caravan arrives, we’re going to be in a real crisis.” Since 2015, Ramos has been collecting testimony from people turned away at the border into San Diego because officials with the C.B.P. claimed the U.S. has reached its capacity for processing asylum seekers. Under Trump, she told me, the situation has worsened, with migrants now waiting as long as four to six weeks to present their asylum claims to immigration agents. In the meantime, the streets and shelters in Tijuana, many of which are in close proximity to cartel houses and smugglers’ dens, have grown overcrowded; the local police and federal soldiers patrolling the city are notoriously corrupt as well. The migrants, Ramos told me, are “sitting ducks.” Blocking ports of entry, she added, “is creating its own lawlessness, and it’s forced people to try to cross who then get penalized” for bypassing the ports of entry.

Mejía had just arrived in Tijuana when we spoke on Monday, but he was clear-eyed about his own prospects. A group of lawyers were advising him about when, exactly, he should report to the port of entry, and he was prepared for delays. “If we have to wait a while, fine,” he told me. “For people like me who don’t have the money to pay a smuggler to come to the U.S., the caravan is what we have. This has been our option. We don’t have to pay, but we have to suffer. And we’ve been through so much already, why not wait a little longer.”