President Trump announced Wednesday he will nominate Kirstjen Nielsen to replace John Kelly as the head of the Department of Homeland Security after the latter left the post to become Trump's chief of staff, Politico reports. Nielsen is an attorney and cybersecurity expert who served in the Transportation Security Administration and on the White House Homeland Security Council under the second President Bush. She was Kelly's second in command at both the White House and DHS, and Kelly was said to be pushing Trump to nominate her. The New York Times states Nielsen is "known as a no-nonsense player and policy wonk" whose style has "frustrated" some people close to Trump during her time at the White House. A number of senior White House officials say her move to DHS would solve some workplace issues for them. (More Department of Homeland Security stories.)