HOMESTEAD, Fla. — Democratic presidential candidates seized Wednesday on renewed national attention to conditions at the southern U.S. border, rushing to visit a children’s migrant shelter to denounce the Trump administration’s treatment of immigrants.

Sen. Elizabeth Warren traveled to a shelter here just 20 miles from the site of Wednesday’s first presidential debate to rally support for immigrants. Former Texas congressman Beto O’Rourke will travel to the Homestead site on Thursday, and other candidates were planning separate visits.

A harrowing photo of a migrant father and his toddler daughter lying face down in the Rio Grande, after drowning while attempting to reach the U.S. border, surfaced this week. It followed reports that grade-school-age children were caring for unattended toddlers in overcrowded U.S. government-funded facilities in Texas. A viral video showed a government lawyer contending that soap and toothbrushes were not necessary in order for the facilities to be safe and secure for the children.

“Trump is responsible for these deaths,” O’Rourke said Tuesday night on Twitter, referring to the father and daughter.

Homestead is not one of the shelters that has made headlines for unsafe conditions, but it has been a popular backdrop for opposition to the Trump administration’s widely criticized family separation policies.

One year ago Wednesday, hundreds of people rallied and demonstrated in opposition to the administration’s zero tolerance policy, which resulted in thousands of migrant children being put in shelters like Homestead while their parents waited in a detention cell for their immigration court hearing.

The latest developments drew fresh anger from Democratic candidates.

O’Rourke, who represented a large swath of the Texas border with Mexico, was the first presidential candidate to announce that he’d couple the Miami debate with a visit to the Homestead shelter. Local activists are leading a group to a protest camp a few yards from the entrance to the shelter where thousands of teenagers are being held at a temporary, for-profit detention center after coming to this country seeking refuge.

Warren was the first Democrat to arrive there Wednesday morning, joining a protest that had been in place for months. She climbed to the top of a ladder, which had been set up across the road from where the detained children were being held so that visitors could see inside. Warren hugged a girl who had been part of the protests and waved to detainees who were playing soccer under the sweltering sun.

The Massachusetts senator was frequently stopped by activists who thanked her, hugged her, or rooted on her presidential bid.

“On behalf of my undocumented family members, thank you so much,” said Stephanie Hernandez, a 21-year-old activist from Miami, who said she had been coming to the camp for “years.”

“Oh, thank you,” Warren said.

Surrounded by reporters, Warren moved toward the protesters’ camp — a series of small canopies where activists had huddled with signs, food, and water. One sign listed the board members of Caliburn International, the owner of the facility; others read “free the children.”

“We will stay here at Homestead until this facility releases these children and closes down,” Warren said. “We start by saying that we do not lock people up for money; we follow up by saying, we do not lock people up for political ends, which is what the president of the United States is doing here.”

Moments after Warren left the site, Jane Sanders, wife of Vermont Sen. Bernie Sanders (I), arrived.

“I wanted to see this and amplify their voices,” Sanders said, referring to the activists walking her through the site.

As she walked to the entrance of the facility, Sanders noted that the senator had voted against the creation of Immigration and Customs Enforcement.

“What he anticipated with it has come true and actually gotten worse,” she said. “We need a complete overhaul of our immigration system. Hopefully, by the time the presidential election comes, we will have closed these detention facilities. But if not, it will be his first executive order,” Sanders said of her husband, who is a presidential candidate.

Sen. Amy Klobuchar (D-Minn.) visited later in the day, and Sen. Kamala D. Harris (D-Calif.) said she was planning to appear Friday. South Bend, Ind., Mayor Pete Buttigieg, former San Antonio mayor Julián Castro and Sen. Kirsten Gillibrand (D-N.Y.) announced visits this week as well.

“If you can look at a picture like that and say that it is acceptable to continue doing what we’ve been doing, then I just don’t understand,” Buttigieg said in an interview on MSNBC.

The Trump campaign sent a preemptive email before the Democrats arrived, highlighting a news story from 2016 — before Trump was president — that presented Homestead in a favorable light. Asked about the photo of the father and daughter, Trump told reporters outside the White House that the deaths wouldn’t have happened if Democrats had fixed immigration laws. He also said the Rio Grande “can be a very rough river of sorts.”

A Gallup poll released Friday showed 23 percent of Americans see immigration as the nation’s top problem, second only to concerns about poor leadership and government — the highest level of concern about immigration since Gallup began tracking the issue in the early 1990s.

The heightened interest, however, seems driven mostly by rhetoric from Trump, who has been warning about criminals coming from Mexico since the first day of his presidential campaign. Only 7 percent of Democrats cite immigration as the nation’s most pressing problem, compared to 42 percent of Republicans.

Vielka Wambold, the Charlotte County chapter president of the Democratic Hispanic Caucus of Florida, had visited the site three times in the past few months. She said she has watched what were once van loads of children grow to busloads.

Wambold said she has also been asking candidates to visit, in part because of their influence, and in part because of the media coverage they bring.

“What I would tell the Democrats is, you can’t expect people to show up for you if you, yourself, don’t show up,” Wambold said. “And what I tell my Latino brothers and sisters is if we don’t come to the table, we don’t have a voice. That means voting. So everything comes right down to getting people to vote in 2020.”

Weigel and Janes reported from Homestead, Fla. Itkowitz reported from Washington. Scott Clement, Jenna Johnson and Dan Balz contributed to this story.