Yuri Gripas / Reuters

President Donald Trump’s postelection purge is poised to continue apace. First, the frequent Trump target Attorney General Jeff Sessions was unceremoniously ejected from office. Now, according to The Washington Post, the frequent Trump target Kirstjen Nielsen, the secretary of homeland security, is likely to be fired in the next few weeks.

“The president has grumbled for months about what he views as Nielsen’s lackluster performance on immigration enforcement and is believed to be looking for a replacement who will implement his policy ideas with more alacrity,” the Post reports, noting that Trump canceled a visit to troops on the Mexican border with Nielsen this week. (Of course, Trump’s decisions over the past few days show that it doesn’t take much to get him to cancel a visit to the military.)

There’s been no shortage of leaks about Trump’s displeasure with Nielsen. The president, as Lindsey Graham likes to repeat, deserves to have Cabinet members in whom he has faith. And whereas Sessions’s ouster raised concerns among people who thought it was a way to topple Special Counsel Robert Mueller, hardly anyone will mourn Nielsen’s demise. But if Trump thinks replacing her will fix his immigration policy, he has a rude surprise coming.

That’s because the problem isn’t Nielsen’s ability to execute on Trump’s immigration policies. The problem is the immigration policies themselves. For the most part, they are impractical, ineffective, or illegal, and they are designed to solve phantom problems.

Consider Trump’s recent panic over the caravan of immigrants slowly wending its way northward through Mexico. First, the group is far away from the United States—still roughly 1,500 miles from the consensus destination of Tijuana. Second, it is numerically small compared with the overall picture of illegal immigration. (Border Patrol apprehended a little more than 300,000 people at the border in 2017; the caravan is estimated to be in the single-digit thousands.) Third, despite Trump’s fearmongering, illegal immigration continues to decline.

But there is illegal immigration, even if the scale is not commensurate to Trump’s rhetoric. The problem there is that the policies Trump wants aren’t effective or practicable. There’s the border wall, which experts say is unlikely to stop immigration, and which in any case would take years and billions of dollars to construct—billions of dollars that Congress refuses to appropriate, a barrier that’s out of Nielsen’s control.

In the absence of the wall, and as part of his preelection immigration-messaging push, Trump ordered at least 5,200 soldiers to the border in October—roughly the same number as U.S. service members in Iraq—and has said that number could reach 15,000. But it’s unclear what their purpose is. They can’t apprehend border crossers, so their role is in support and administration. Moreover, the caravan is still hundreds of miles away. So as Thomas Gibbons-Neff and Helene Cooper report, the deployed troops are sitting around in brutal heat, eating MREs, without much to do, and it’s costing taxpayers millions of dollars.

Trump has also announced plans to drastically curtail asylum applications at the border. But no matter how draconian the administration’s policies are, they don’t deter all the immigrants headed northward. Members of the caravan aren’t unaware of Trump’s views, but they’re desperate enough to try to reach the U.S. anyway. Nielsen doesn’t have control over the “push” factors that drive immigrants from their homes, especially those from the Northern Triangle.

Besides, as Dara Lind reports, it’s unclear whether the new asylum restrictions are legal. If they fail to stand up in court, they’d join a string of previous Trump immigration policies struck down by judges. The Supreme Court finally approved a much-reduced version of Trump’s Muslim travel ban after lower courts rejected earlier, more sweeping versions. The administration’s decision to separate children from their parents at the border also drew a flurry of litigation, though political pressure forced the White House to withdraw the policy before any court could. When the administration then announced it would attempt to incarcerate children in violation of an existing court agreement, a judge slapped the move down. Once again, there’s nothing Nielsen can do about any of this.

Trump has pushed Nielsen to do more. For example, he’s toyed with the idea of closing the border altogether, which might or might not be illegal but would in any case be a logistical and practical nightmare. Explaining this sort of thing to the president only makes him dislike and distrust Nielsen more.

At the root of the conflict between Nielsen and Trump is the president’s general distrust of her as not a member of his ideological team. She is an immigration hard-liner, but she previously worked in the George W. Bush administration, a red flag for Trump.

Trump’s aides can generally be divided into two factions: true believers and managers. The first group are Trump backers, while the others are technocrats focused on running government departments. Secretary of State Mike Pompeo is a true believer; his predecessor, Rex Tillerson, was pushed out because he was a manager. Secretary of Defense James Mattis is a manager. Sessions began as a true believer who proved too much of a manager for Trump’s tastes for refusing to railroad the Russia probe.

Nielsen, with her Bush pedigree and her comparatively cautious approach to implementation, is theoretically a manager, though the debacle of the child-separation policy shows that she hasn’t been an especially effective administrator. Nielsen stood at the White House lectern and tried to claim there was “not a policy” of family separation when not only was it manifestly clear that there was, but other administration members had said there was. It seems likely that if Trump fires Nielsen, he will try to replace her with more of a true believer.

Whereas some Trump critics who disliked Sessions were worried that Trump was firing him just to get to Mueller, there’s no reason to expect such a groundswell of support for Nielsen. Her hard-line policies are detested by progressive immigration watchers, but she hasn’t been effective enough to win over Trump loyalists. The only person who seems to be standing up for her is White House Chief of Staff John Kelly, who preceded her at the Department of Homeland Security and then helped install her as secretary.

Yet Kelly’s own position is tenuous, so that may not help Nielsen. ABC News reported Tuesday that Trump is close to axing Kelly. Rumors of Kelly’s demise have circulated for more than a year now; Tillerson hung on well after he was seen as a lame duck, too, so it’s possible Nielsen might survive simply due to Trump’s hatred of actually firing anyone. If so, immigration policy will keep limping along.

Or else Trump will follow through and get rid of Nielsen, replacing her with a true believer. And if he does? A new secretary is likely to be just as hamstrung by the impracticalities and illegalities of Trump’s policy ideas as his predecessor has been.

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