Homeland Security Secretary John Kelly’s move to White House chief of staff is ushering in a cloud of uncertainty at the department that has led some of President Donald Trump’s most controversial undertakings — from its roundup of undocumented immigrants to his travel ban and proposed border wall.

It may also set the stage for a brutal confirmation fight if President Donald Trump tries to replace the retired Marine general with an outspoken opponent of illegal immigration instead of a seasoned bureaucrat or lawmaker.


A person close to Kelly said it's unclear who will replace him.

But several White House and former DHS officials proffered a slate of names of possible replacements for Kelly, with Texas Rep. Michael McCaul, the Republican chairman of the House Homeland Security Committee, emerging as a leading candidate.

Other potential picks include Thomas Homan, acting director of U.S. Immigration and Customs Enforcement, who accompanied Trump on Air Force One on Friday, and Kansas Secretary of State Kris Kobach, an outspoken opponent of illegal immigration who is helping to lead the president's controversial commission on alleged voter fraud.

Separately, department staffers have been talking about the possibility that the role might go to Attorney General Jeff Sessions, according to two sources with contacts at DHS, but a person close to the Trump administration said he's unlikely to get the job.

Which direction Trump takes could have a dramatic effect on soothing or stoking the uncertainty gripping his White House.

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"So much of Trump's agenda is tied to DHS," said one Republican lobbyist close to the White House. The consultant added: "Kelly was one of the best decisions he has made thus far. Considering how central DHS is to his agenda, he's got to make another great decision."

Homan got praise from one former DHS official, who called him “a career tough guy” who “plays right to Trump's sweet spot.” ICE is the agency leading Trump’s street-level enforcement push, and Homan traveled with Trump on Friday to Long Island, N.Y., where the president spoke about the link between street gangs and illegal immigration.

Kobach, on the other hand, would ignite a firestorm among Democrats, who accuse him of carrying out an agenda of denying voting rights to minorities. Seth Stodder, who held assistant secretary roles at the Homeland Security Department from 2015 to this year, said a Kobach pick would be “radioactive.”

“It would be one hell of a confirmation hearing,” Stodder said, adding that he would probably oppose the nomination himself. “I just can’t imagine that happening.”

Picking Sessions, meanwhile, would empower Trump to select a new attorney general who could exert more control over the Russia probe, perhaps an ally like Rudy Giuliani. But that option would likely set up a major clash with senators of both parties.

One source familiar with the process cautioned that it's "very early," and things could change in the coming hours and days.

For now, the department announced Friday, Kelly will remain in his DHS role through Monday. After that, Deputy Secretary Elaine Duke — a Kelly confidante and well-respected leader — will become acting secretary.

Duke, who previously worked as DHS undersecretary for management from 2008 to 2010, would be a capable choice in the eyes of some former DHS officials. Juliette Kayyem, a former assistant secretary for Homeland Security in the Obama administration, called her smart but not overly political, a good mix for the department. Still, she’s skeptical Duke would get the nod.

“[You] couldn't meet a nicer person who has nurtured and managed that department for three different presidents,” Kayyem said. “Trump doesn't want nice.”

Blain Rethmeier, the sherpa who guided Kelly through his confirmation hearing, said that “nobody is better or smarter on the policy” than Duke, but that “she isn't a known brand to the public.”

Trump's choice for the next secretary will be crucial, and not only because of the agency’s sprawling portfolio, which includes border security and visa processing along with airport security and disaster relief.

Kelly successfully piloted the president’s immigration crackdown under his watch: ICE has arrested roughly 75,000 undocumented residents to date. At the same time, reports of people trying to enter the U.S. illegally have fallen dramatically. Now Kelly's departure for the West Wing will leave a void as the department deals with the details of enforcing Trump’s travel ban, his proposed border wall and terrorist threats against aviation.

Kelly is seen inside and outside the White House as a capable manager. Even some Democrats see him as the most palatable member of the Cabinet. But that is likely to change once he enters the White House, where he'll become a political target for the left.

McCaul, meanwhile, may have the easiest path toward being confirmed as Kelly’s replacement.

The Texas Republican competed for the secretary role in November. He introduced an immigration bill on Friday that would provide $10 billion for Trump’s border “wall,” a pot of funds that would pay for a mix of wall, fence, technology and aerial surveillance over four years, while boosting Border Patrol by 5,000 agents — the level Trump called for in a January executive order.

McCaul even published an op-ed on Fox News in December that pledge his support for Trump’s signature project.

“We are going to build the wall. Period,” he wrote. “In the process, I pledge to stand side-by-side with the Trump administration to throw out Obama’s reckless immigration policies and start enforcing our nation’s laws.”

He followed up Friday with another Fox op-ed that praised Trump's approach to foreign policy as "strong and decisive."

"The Trump White House relishes American exceptionalism and enjoys promoting Western values," McCaul wrote, citing examples such as his handling of ISIS. "It clearly understands that there is no such thing as leading from behind when it comes to tackling the most pressing international security issues."

Still, the congressman faced backlash from border hawks when his name was floated for the DHS role after the election. Activists in favor of lower immigration levels tweeted under the hashtag "#NeverMcCaul" and derided him as soft on the issue.

Daniel Lippman contributed to this report.