OPINION: Kirstjen Nielsen Enforced Cruelty at the Border. Her Replacement Could Be Worse.

She will be remembered for the forced separation of thousands of migrant families.

Time finally ran out for Kirstjen Nielsen, President Trump’s beleaguered secretary of homeland security.

The terms of Ms. Nielsen’s departure were unclear. She met with the president on Sunday evening to discuss continuing problems at the southern border. At the conclusion of the meeting, Mr. Trump said on Twitter that Ms. Nielsen “will be leaving her position” and thanked her for her service, implying he had asked her to step down. Ms. Nielsen issued a formal letter...