WASHINGTON — President Trump nominated Kirstjen Nielsen, a deputy to White House Chief of Staff John Kelly, to be Homeland Security secretary on Wednesday, filling the vacancy left by Kelly when he took his current post in late July.

"Ms. Nielsen has extensive professional experience in the areas of homeland security policy and strategy, cybersecurity, critical infrastructure, and emergency management," the White House said in a statement announcing the nomination.

Nielsen, 45, is currently a deputy to Kelly at the White House, a position she has held officially for about a month, although she came to the White House with Kelly in July.

An attorney with experience in cybersecurity and homeland security, Nielsen worked as Kelly’s chief of staff at the Department of Homeland Security before following him to work for Trump as principal deputy White House chief of staff.

If confirmed by the Senate, Nielsen would be the first former employee to run the department created in the wake of the terrorist attacks of Sept. 11, 2001.

Previously, she worked at the Transportation Security Administration and on the White House Homeland Security Council under President George W. Bush.

Nielsen's experience with the Bush administration worries Rep. Bennie Thompson of Mississippi, the top Democrat on the House Homeland Security Committee.

Thompson cited the Bush administration's "botched" response to Hurricane Katrina in 2005 and expressed concern that Trump and Homeland Security have not learned from the lessons of the responses to hurricanes that wiped out Puerto Rico and the U.S. Virgin Islands.

Natural disaster recovery and relief will be a priority for Nielsen in addition to cyber security, said Fran Townsend, Bush's former homeland security adviser from 2004 to 2008.

"Tough as nails"

Townsend called Nielsen, who worked with her for four years, "tough as nails. She's confident."

If appointed, Nielsen will succeed, Townsend said, because she knows how the White House works, has Kelly's trust and has working relationships with Cabinet secretaries.

Nielsen will be the first of any agency secretary to have a cyber background, which she developed in the White House and private sector, Townsend said.

Since Kelly departed for the White House, Elaine Duke had been running the department on an interim basis, and supervised recent hurricane recovery efforts in Florida, Texas, and Puerto Rico.

"Warm, thoughtful ... intelligent"

Nielsen holds degrees from Georgetown School of Foreign Service and the University of Virginia Law School. She was also a senior fellow at the Center for Cyber and Homeland Security at George Washington University, where she worked closely with Frank Cilluffo, the university's associate vice president.

“Generally speaking I think she’s incredibly thoughtful, a wonk at heart, someone who brings deep knowledge of cyber,” Cilluffo said.

He called her a "great selection" for the job, citing her past experience at the agency allows her to know the place "inside and out."

“She also has a keen awareness and understanding of inter-agency issues,” Cilluffo said, adding that Nielsen "can drill very deep on the substance of issues but can also sort of take a step back and ask why it really matters. I found her to be warm, thoughtful and incredibly intelligent.”

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