By Nick Miroff and Josh Dawsey | Washington Post

WASHINGTON – An attempt by President Donald Trump’s senior adviser Stephen Miller to engineer a new shakeup at the Department of Homeland Security was blocked this week by Kevin McAleenan, the department’s acting secretary, who said he might leave his post unless the situation improved and he was given more control over his agency, administration officials said.

The closed-door clash flared over the fate of Mark Morgan, the former FBI official the president has picked to be the new director of U.S. Immigration and Customs Enforcement.

With Morgan eager to move into the top job at ICE, Miller on Wednesday urged the president to have Morgan installed as the new commissioner of U.S. Customs and Border Protection (CBP) instead.

McAleenan the next day told senior White House officials that he – not Miller – was in charge of the department, said the three Trump administration officials, who spoke on the condition of anonymity to describe internal tensions one Trump aide likened to an “immigration knife fight.” McAleenan also argued that he should make personnel decisions at his agency, or at least be involved in them, these people said, and that communication needed to improve. McAleenan met with Mick Mulvaney, the acting White House chief of staff, among others, the officials said.

McAleenan prevailed in the dispute. Morgan will take over as acting ICE director next week, according to three Homeland Security officials said. Matthew Albence, the current acting director whom Miller wanted to keep in the top role, will return to his job as ICE deputy director.

“This was a power struggle between McAleenan and Miller, and McAleenan won,” said one senior administration official with knowledge of what transpired.

Mulvaney couldn’t be reached for comment. The Department of Homeland Security declined to comment. White House officials said Friday the two men had worked out some of their tensions since the argument.

With DHS facing a spiraling migration crisis at the border and the president this week pitching an immigration overhaul that was panned by lawmakers, the clash in the White House was an indication of the roiling personal battles playing out behind the scenes.

The ongoing influx of migrant families crossing into the United States along its southern border has strained U.S. Border Patrol resources so far beyond capacity that, for the first time, the Trump administration’s border crisis is spilling out into America’s interior. A record number of families have crossed the border in recent months, and unauthorized migration is at its highest level in more than a decade. Trump has declared a “national emergency” over the issue – a contentious declaration that has split along party lines – and has been agitated behind the scenes to make widespread changes.

At Miller’s behest, Trump last month ousted DHS Secretary Kirstjen Nielsen and the previous acting director of ICE, Ronald Vitiello, along with other top officials. He has argued to the president that he needs a different team that will be more aggressive in carrying out his agenda – and has frequently argued in immigration meetings that others are seeking to undercut the president.

Prior to their departure Nielsen and Vitiello had challenged a plan devised by Miller and Albence to carry out mass arrests of migrant parents and children eligible for deportation in 10 U.S. cities. Miller has accused other officials of not writing enough regulations or not being aggressive enough to stop immigrants.

Trump at the time announced he wanted to go in a “tougher direction,” and on May 5 announced Morgan as his pick to replace Vitiello. The decision blindsided Nielsen, who learned from Capitol Hill aides, according to people familiar with the matter. She was dismissed three days later in a Sunday meeting at the White House and replaced by McAleenan in an acting capacity.

When McAleenan was appointed, Miller – who has taken a vast role on immigration policy from his West Wing office – told White House officials and others that he would back McAleenan. The acting secretary worked in the Obama administration and has drawn some bipartisan praise over his two decades in government.

Morgan worked at the FBI under former director James Comey, and was sent to U.S. Customs and Border Protection to lead a use-of-force overhaul. The effort was a success, but made him deeply unpopular in the insular culture of the Border Protection, whose senior leaders chaffed at the sight of an outsider wearing the agency’s green uniform and giving orders.

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Judge: Eric Trump must testify before the election Miller’s attempt this week to install Morgan at CBP – instead of ICE – would have undercut McAleenan and risked a new backlash from CBP leaders. According to two officials, Border Protectionl union chief Brandon Judd joined Miller in the effort to put Morgan at CBP, where he would displace John Sanders, whom McAleenan has placed at the head of the agency. Trump is close with Judd and often asks his opinion on immigration decisions.

Albence is expected to remain at ICE, and will be eligible to retire in eight months, DHS officials said.

Trump’s initial pick of Morgan for the post, announced via Twitter on a Sunday morning, surprised many in the administration and led to a later tweet clarifying the nomination, which requires Senate confirmation