White House Homeland Security chief Nielsen is out Customs and Border Protection Commissioner Kevin McAleenan will become acting DHS secretary.

Kirstjen Nielsen will leave her post as secretary of Homeland Security, President Donald Trump announced on Sunday, highlighting the administration's inner turmoil over rising levels of illegal immigration just days after the president backed off a threat to close the U.S.-Mexico border.

The number of migrants arrested at the border in recent months — a proxy for illegal crossings — has increased to the highest levels in more than a decade. Under Nielsen’s watch, the administration experimented with a range of policies to deter migrants, only to see border arrests continue to rise.


“Secretary of Homeland Security Kirstjen Nielsen will be leaving her position, and I would like to thank her for her service,” Trump wrote on Twitter. “I am pleased to announce that Kevin McAleenan, the current U.S. Customs and Border Protection Commissioner, will become Acting Secretary for @DHSgov. I have confidence that Kevin will do a great job!“

Nielsen oversaw the implementation of Trump’s contentious immigration agenda, including the separation of thousands of families at the U.S.-Mexico border.

The 46-year-old Cabinet member was confirmed to the role in December 2017. Almost from the start, she came under fierce criticism from Trump over an uptick in illegal immigration. As a wave of Central American families arrived at the southwest border in recent months, scrutiny of her performance only intensified.

The news comes after the White House on Friday unexpectedly pulled the nomination of Ronald Vitiello to become director of Immigration and Customs Enforcement. Vitiello, a longtime Border Patrol official, had already been approved by one congressional committee, but still need the approval of the Senate Judiciary Committee and Senate confirmation.

A White House aide said Nielsen was told of the decision to withdraw Vitiello’s nomination two weeks ago, but disagreed with the move.

“I think she thought by stalling on making a plan for new ICE leadership, she would buy time to relitigate the decision,” a senior White House official said.

However, a person familiar with the situation argued that Nielsen was blindsided by the decision to drop Vitiello.

“At the end of the day, there were mounting frustrations on both sides,” the person told POLITICO.

Trump said Friday that his administration sought to “go in a tougher direction“ with the ICE role, but the White House has not announced a new nominee.

A senior administration official aligned with Nielsen said the White House had summoned her to a meeting with the understanding that she would be required to explain the rising arrests on the southwest border. The official said Nielsen didn’t want to plead to maintain her role and chose to resign instead.

Nielsen’s departure, coupled with the decision to abandon Vitiello’s nomination, leaves DHS thin at the leadership level — even as Trump and other officials warn that illegal immigration has reached crisis levels. With McAleenan elevated to acting secretary, Deputy Commissioner Robert Perez of U.S. Customs and Border Protection will probably take over at that agency.

“The system’s at a breaking point,” one congressional aide said. “I’m not sure how adding more chaos and throwing more fuel to the fire is going to be helpful.”

In recent weeks, both Trump and Nielsen have argued that the influx of migrants amounts to a pressing crisis that requires Congress to take action. DHS estimated that border officials encountered 100,000 migrants in March. If that trend continues, arrests this year could resemble the higher levels of the 1980s, 1990s and 2000s. In addition, family members make up a significant number of those crossing the border recently, a situation that presents unique health and safety concerns, according to the administration.

With that in the background, the White House has urged lawmakers to toughen asylum standards and make it easier to detain and deport families and children from El Salvador, Guatemala and Honduras. Democrats have countered that the Trump administration has squandered resources by arresting low-level targets and seeking to detain as many people as possible. They also have ripped Trump for a recent move to cut hundreds of billions of dollars in assistance to Central American countries as a punishment for failing to stop migrant outflows.

The names of several possible candidates to replace Nielsen surfaced Sunday. Rick Perry, the current energy secretary and a former Texas governor, and former Virginia Attorney General Ken Cuccinelli have both been discussed as possible candidates, according to the aide.

Another name in the mix is Emilio Gonzalez, city manager of Miami, according to a former DHS official. Gonzalez was director of U.S. Citizenship and Immigration Services during the administration of President George W. Bush.

The president was widely expected to dismiss Nielsen after November’s midterm elections and surprised allies by keeping her on board. The two have clashed on their approach to immigration and border security from the outset of her tenure, with Trump complaining that she was too soft and regularly pushing her to take measures that crossed legal boundaries, she told allies.

In a resignation letter published online, Nielsen touted the administration’s performance, despite the soaring numbers of border arrests.

“I can say with confidence our homeland is safer today than when I joined the administration,” she said. “We have taken unprecedented action to protect Americans. We have implemented historic efforts to defend our borders, combat illegal immigration, obstruct the inflow of drugs, and uphold our laws and values.”

The letter said she would resign as of April 7, but Nielsen tweeted late Sunday night that she would continue as secretary through Wednesday to facilitate the transition. An initial draft provided to POLITICO misstated the year as 2018.

Democrats repeatedly sparred with Nielsen during her tenure as secretary and fumed at her department’s decision to split apart thousands of migrant families under the “zero tolerance” policy that ran from April to June of last year.

"Hampered by misstep after misstep, Kirstjen Nielsen's tenure at the Department of Homeland Security was a disaster from the start,” Rep. Bennie Thompson (D-Miss.), chairman of the House Homeland Security Committee, said in a written statement following Trump‘s tweet. “It is clearer now than ever that the Trump administration's border security and immigration policies — that she enacted and helped craft — have been an abysmal failure and have helped create the humanitarian crisis at the border.“

Senate Minority Leader Chuck Schumer argued that Nielsen’s departure signaled that Trump had moved far outside the mainstream when it comes to immigration enforcement.

“When even the most radical voices in the administration aren’t radical enough for President Trump, you know he’s completely lost touch with the American people,” Schumer said in a statement.

Nielsen lost two allies within the Trump administration at the end of 2018: White House chief of staff John Kelly and Secretary of Defense James Mattis, whose departures came after a lengthy record of clashes with the president.

Kelly, who preceded Nielsen as DHS secretary, was a mentor to Nielsen, who was his chief of staff at DHS and later his White House deputy.

Still, her alliance with Kelly didn’t shield her from the president’s ire over migrant “caravans” that trekked to the border from Central America over the past year. Nielsen teetered on the brink of resignation in May after Trump blasted her border management during a Cabinet meeting. Six months later, Kelly and national security adviser John Bolton engaged in a heated conversation outside the Oval Office over Nielsen’s approach to securing the border.

The announcement that McAleenan would assume the secretary’s role in an acting capacity surprised some former DHS officials. According to the department’s line of succession outlined in a 2017 defense spending bill, Claire Grady, the undersecretary for management, would be the next in line to helm the department.

Grady is currently the acting deputy secretary, a position that has remained vacant since former deputy Elaine Duke retired last April — one of numerous top positions that remain filled by acting officials at DHS.

One person familiar with Nielsen’s departure wondered whether McAleenan could win Trump’s approval in the short or long term, and contrasted his measured style with former acting ICE Director Thomas Homan’s brash persona.

"Kevin’s a smart guy, but he’s not like Tom Homan, like a rabble rouser,” the person said. “Kevin is very thoughtful and deliberate.”

Roger Dow, president of the U.S. Travel Association, praised McAleenan’s appointment and history of facilitating legal trade. McAleenan served as both deputy commission during the Obama administration and became acting commissioner when Trump took office. He was confirmed as commissioner in March 2018.

“In Mr. McAleenan we have an ally with a full and complete understanding of both national security and the importance of facilitating cross-border trade, which includes travel,” Dow said.

Amid Trump’s busy immigration agenda, Nielsen remains best known for her involvement with the zero-tolerance policy and resultant family separations.

The policy called for all suspected border crossers — including parents and asylum seekers — to be prosecuted for illegal entry. As a result, thousands of children were separated from their parents, with children classified as “unaccompanied.“

Nielsen eventually helped Trump draft an executive order barring family separations, but 10 months and several legal challenges later the administration is still struggling to deal with the fallout.

Nielsen has repeatedly said the Trump administration never had a family separation policy, a semantic dodge undermined by the reality of increased separations at the border.

A DHS internal watchdog report released in late October said Nielsen and other officials from DHS and the Health and Human Services Department were blindsided by then-Attorney General Jeff Sessions' initial decision to implement zero tolerance.

Daniel Lippman, Anita Kumar, and Gabby Orr contributed reporting.

CORRECTION: An earlier version of this article gave an incorrect title for Ken Cuccinelli. He is the former attorney general of Virginia.