EL PASO — The delegation of Democratic lawmakers jostled for space in the cramped room in the border processing center, straining to hear over the sounds of crinkling mylar blankets and a crying baby, as a Venezuelan migrant told her grim story.
They listened sympathetically as the woman told of the weeks she would have to spend in Mexico before her next asylum hearing, at which she would try to explain the violence she had faced at home that had forced her to leave.
“You should not have to go back to Venezuela,” Representative Tom Malinowski, Democrat of New Jersey and a former State Department official, said, his voice tight with anger. “And you should not be stuck in Mexico. I think we all would agree with those two statements.”
Hours before, Representative Duncan Hunter, Republican of California, had posted a video on Twitter from a different Border Patrol facility in Texas, offering a rosier picture of what was happening to migrants at the border.
“It’s basically a Walmart,” he said, gesturing across neatly organized crates of toothpaste and soap. “It’s incredible how well we’re treating people who are here illegally, how well we’re taking care of them.”
The two disparate reactions reflect the opposing poles of an intractable immigration debate that has raged ever more intensely in recent months, as President Trump’s policies have grown more aggressive and migrant detention facilities have strained under the burden.
In the past six months, dozens of members of Congress and their aides have descended upon the southwestern border in an effort to see what is happening there. To witness the visits is to understand the nub of the deep divide over how to repair the nation’s broken immigration system.
The fact-finding tours, detailed in interviews with more than two dozen lawmakers and aides, are sometimes sanitized for the V.I.P.s who take them, as the Trump administration works to put the best face on an often inhumane situation. But they have yielded moments of raw emotion and glimpses of human suffering that have prompted passionate testimony, viral videos of lawmakers on their tours, new legislative proposals and, in one case, a book.
Every lawmaker who makes the trek south agrees on the system’s dysfunction, but few emerge with changed minds or drastically different perspectives. The bigger question of how to avoid having the immigration crisis once again languish remains unanswered.
The Democrat-led House this week approved two bills largely on party lines that would hold the Department of Homeland Security to higher accountability and medical standards for immigrant holding facilities, but its chances in the Republican-held Senate are slim to none. And in a committee hearing over funding the border, senators clashed over how much money to give to the president’s wall at the southwestern border, even after the chamber’s majority voted to end his national emergency declaration there.
“The goal was, everybody could see it and say, ‘O.K., we’ve all seen it. We can come to a common set of conclusions on how to be able to resolve it,’” Senator James Lankford, Republican of Oklahoma, said of his recent visit to the border. “But I’m not hearing that.”
“Maybe, lessons learned.”
What lawmakers take away from the border usually depends on what they are looking for.
Representative Andy Biggs, Republican of Arizona, organized multiple summer trips focusing on the enforcement side, giving lawmakers the chance to tour fragments of Mr. Trump’s border wall and to speak with local law enforcement, as well as with property owners whose land runs close to the border.
Democrats tend to focus instead on the humanitarian side. Representative Veronica Escobar of Texas has led several groups to her El Paso district, organizing interviews with migrants detained in Juárez, Mexico, and taking her colleagues to the road between the two countries.
There are politics involved even in the rosters of the groups. In July, Senate Democrats refused to join Vice President Mike Pence and Republican senators for a trip to a facility in McAllen, Tex., ultimately fearing, in the words of Senator Richard J. Durbin, Democrat of Illinois, “getting overwhelmed by Pence and his public relations.”
“There’s a tension here between Trump supporters and critics, Republicans and Democrats, about these detainees and the people who are in the process,” Mr. Durbin said. “This tension is going on between humane treatment and deterrence.”
Even trips like the one taken by the bipartisan Problem Solvers Caucus, where Republicans and Democrats huddled afterward to share impressions and ideas, have done little to move the dialogue forward.
Outside the Border Patrol’s central processing center in McAllen, Senator Brian Schatz, Democrat of Hawaii, recounted a conversation he had in broken Spanish with a Salvadoran woman about her 5-year-old daughter. While the girl had told Mr. Schatz she had just eaten, her mother told him that was not true.
“She said, ‘She’s not eating,’” Mr. Schatz said, choking back tears. “These kids are being traumatized, and they’re doing it on purpose,” he said of the Trump administration.
In a holding facility in Donna, Tex., after listening to a Central American woman who was cradling her 2-month-old while detailing her trip across a river to the United States, Senator Chuck Schumer, Democrat of New York and the minority leader, exasperated, turned to his colleagues and said, “These aren’t drug dealers.”
Lawmakers who have made multiple trips to the border said that they have seen some improvement over the past few months, in part because the number of migrants trying to enter the country had gone down, but also because of the outrage over reports of decrepit conditions and poor health care.
“What I saw between now and a year ago were more facilities that are aimed at the humanitarian care issue,” said Senator Shelley Moore Capito, Republican of West Virginia, who toured portions of the border this month with two Republican colleagues. “Maybe, lessons learned.”
“I think I can assess pretty clearly the conditions.”
The border tours that lawmakers and members of the news media receive are often sanitized to present the best possible conditions: As soon as visits are planned, preparations begin inside the Trump administration’s detention facilities.
Routes are planned to avoid messy spaces like laundry rooms as well as some special housing units where detainees are held in solitary confinement, according to a former detention official at Immigration and Customs Enforcement, who spoke on the condition of anonymity for fear of retribution. Staff is instructed to brief visitors on the requirements for things like medical care, sanitation and food — giving the impression that they are following the rules, even if the facility is failing to comply, the official said. The agency did not respond to a request for comment.
Before the tours, the official added, the orders that detainees receive are much simpler: Do not speak to visitors.
They are also told to put on their full uniforms, which typically resemble hospital scrubs, and to avoid being seen in the stripped-down attire that is common in hot or crowded facilities. When small groups of reporters and lawmakers are allowed inside, they are frequently asked to leave their cellphones behind and not speak to any of the migrants in custody.
Some Republicans say that because they can see the population levels and available supplies, they see no need to push back on the request not to speak to migrants.
“I’m not sure that I need to interview detainees, necessarily. I think I can assess pretty clearly the conditions,” said Mr. Biggs of Arizona, who is in line to be the next chairman of the ultraconservative House Freedom Caucus. “I’m not sure that you need to interview somebody to fully assess that.”
To reporters last month at the ICE processing center in El Paso, officials were careful to emphasize the extent of care offered to migrants, as they walked past framed health accreditation certificates lining some of the hallways. They argued that the facility should not be seen as a prison because the migrants, made to wear color-coded outfits designating the severity of their criminal history and the offenses they were accused of committing, had not been sentenced by an American judge.
If pressured by lawmakers and their staff, permission to speak to some migrants can be negotiated in advance. But it can also be revoked, heightening tensions with lawmakers responsible for oversight of the facilities.
The Department of Homeland Security canceled 11 visits scheduled by the House Oversight Committee’s staff to a number of facilities across the country in August, citing a lack of cooperation from congressional aides. (The committee’s chairman, Representative Elijah E. Cummings of Maryland, disputed the allegations.)
Officials also refused to allow a Democratic delegation, which included Mr. Malinowski and Ms. Escobar, to visit with two men who were on a hunger strike in the El Paso facility.
At the time, one of those men, Ajay Kumar, was kept in conditions that one California doctor who reviewed Mr. Kumar’s medical records deemed to be “markedly below standard of care, and putting his life at risk,” according to an affidavit made public in late August. Officials during the visit declined to comment on the conditions of the strikers, citing the court order and privacy restrictions.
The doctor, Parveen Parmar, wrote that the treatment of Mr. Kumar “would never be tolerated in any hospital and is, frankly, the worst medical care I have seen in my 10 years of practice.”
Mr. Kumar, according to his lawyer, was released from ICE custody this week.
Lawmakers say such allegations only deepen their determination to see for themselves what is actually happening at the border.
“When somebody puts up roadblocks,” Ms. Escobar said, “of course you’re going to get suspicious, and there’s going to be mistrust.”
Caitlin Dickerson contributed reporting from New York.