Former Secretary of State Hillary ClintonHillary Diane Rodham ClintonAre Democrats turning Trump-like? The Hill's Campaign Report: Battle for Senate begins to take shape The Hill's Morning Report — Trump and the new Israel-'squad' controversy MORE on Monday said that the Trump administration's treatment of migrants will remain unchanged despite Kirstjen NielsenKirstjen Michele NielsenTrump casts uncertainty over top intelligence role Juan Williams: Trump, his allies and the betrayal of America Trump taps Texas Rep. Ratcliffe to replace Dan Coats as top intelligence official MORE's resignation as Homeland Security secretary.

“Let's be clear: This administration's dehumanization and cruelty toward migrants will not stop after Kirstjen Nielsen leaves office. It is their principal policy," the 2016 Democratic presidential nominee tweeted.


Trump announced Nielsen's resignation Sunday, promoting Kevin McAleenan to acting secretary of the Department of Homeland Security.


Nielsen was the public face of the Trump administration's "zero tolerance" immigration policy that drew widespread criticism last summer.

The policy resulted in thousands of children being separated from their families at the border.

Several commentators and politicians have said that Nielsen will be remembered primarily for her role in that policy.