WASHINGTON >> President Donald Trump has selected Kirstjen Nielsen, a top White House aide and a former homeland security official in the George W. Bush administration, to lead the Department of Homeland Security, according to two senior administration officials and another person familiar with the decision.

Trump could announce his choice as soon as today, the people said, speaking on condition of anonymity because they were not authorized to make it public. Nielsen’s selection was first reported by Politico.

Nielsen would replace John F. Kelly, who left the department in July to serve as the chief of staff in Trump’s chaotic White House. Kelly had drafted Nielsen to be his chief of staff at the Homeland Security, and when the president plucked him to serve in the West Wing, he brought her to the White House as his No. 2.

In elevating Nielsen, Trump is installing a policy expert with deep experience in the Department of Homeland Security’s mission, including immigration enforcement, disaster response and cybersecurity. But he would also remove from his White House a person who brought a regimented style to a freewheeling and often dysfunctional West Wing, much to the chagrin of some senior officials and people close to the president who chafed under her dictates.

Kelly, who has relied on Nielsen’s counsel and expertise since he was preparing for his January confirmation hearing to be homeland security secretary, had pushed hard for her selection. Former colleagues said on Wednesday that she was well-qualified.

“She’s a total homeland security expert — absolutely has no learning curve,” said Michael Allen, who worked with Nielsen during the Bush administration. “She’s an experienced manager, she’s an implementer, she knows how to get under the hood and figure out what needs to be connected to what.”

Added Frances Townsend, her boss at the White House during the Bush administration: “She is tough as nails, competent and has rightly earned the president’s respect.”