If the abrupt resignation of Department of Homeland Security Secretary Kirstjen Nielsen raised eyebrows among the G.O.P., the firing of Secret Service Director Randolph Alles, coupled with rumors that Donald Trump is toying with a “purge” at D.H.S., escalated its fears into full-on panic. “They are doing in an intellectual-like way what the president wants to accomplish. So no, they should not go,” Senator Chuck Grassley told Politico on Monday, referring to U.S. Citizenship and Immigration Services Director Lee Francis Cissna and U.S.C.I.S. Office of Policy and Strategy chief Kathy Nuebel Kovarik, two officials reportedly in Stephen Miller’s crosshairs. Grassley repeated his warning to The Washington Post. “He’s pulling the rug out from the very people that are trying to help him accomplish his goal” of stronger border security, he said, adding that he would take his plea to Fox News, where the president would be certain to hear it.

Grassley’s full-court press is among the clearest efforts by Republicans to save Trump from his own worst instincts on immigration. The president’s policies proved wildly unpopular in the 2018 midterms, contributing to the Democrats’ resurgence in the House, and his recent attempt to secure wall money by shutting down the federal government did nothing to endear him to the American public. Just last week, Trump’s threat to shut down the U.S.-Mexico border—a move that experts said would invite economic chaos—prompted Republicans to worry they had another P.R. disaster on their hands. “I understand the president’s frustration,” Texas Senator John Cornyn told reporters at the time. “But the unintended consequences of that would be bad for everybody: economic, diplomatic.”

Now, with D.H.S. leadership ravaged and the president contemplating a veritable assault on immigrants and asylum seekers, Republicans are again attempting to talk him off the ledge. Though many empathize with Trump’s frustration over the mounting number of migrants at the border, several are fretting that ousting Nielsen was counterproductive. Senator John Kennedy called the White House response to her resignation “classless”; Senator Joni Ernst expressed the need for “continuity” at the top of D.H.S.; and Senator Ron Johnson, the chairman of the Homeland Security Committee, bluntly said that he was “concerned with [the] growing leadership void.” There were also hints at a hardening distaste for Miller: some voices in the administration, Cornyn told The Hill, “are creating more problems for the administration by losing senior leadership in these important positions. That’s bound to make the president’s and the administration’s job harder.”

“I think it would be hard for [Miller] to demonstrate he’s accomplished anything for the president,” Grassley quipped to the Post. When asked to elaborate, he shot back, “It’s pretty hard to elaborate on it when there hasn’t been any accomplishments.”

Their biggest concern isn’t the leadership void, however, but rather that Trump might force Nielsen’s replacement to bring back the extremely unpopular family-separation policy. Shortly after news of Nielsen’s departure broke, NBC News reported that Trump had pressed her for months to reinstate “large-scale” child separation, seemingly convinced that it was “the most effective policy” in deterring illegal border crossings. Though Nielsen resisted, her acting replacement, Kevin McAleenan, has expressed support for a “binary choice” model—letting parents choose between losing their children or bringing them into long-term detention—that Senate Republicans consider a nonstarter. “One thing we all agree on now is families ought to be kept together as much as possible,” said Cornyn, and a Senate G.O.P. aide suggested to The Hill that there would be bipartisan opposition to any nominee who wanted to revisit child separation. “If Trump wants to reinstate the family-separation policy, that would be met with a lot of resistance,” the aide said. “If he’s looking for a D.H.S. secretary to do that for him, that would be a cluster.”