Nielsen, a cybersecurity expert who served as Kelly's chief of staff when he was DHS secretary, accompanied him to the White House as his deputy and quickly emerged as a controversial presence.
The White House hasn't made an official announcement on Nielsen's nomination as of publication.
Anderson Cooper, Andy Cohen to Co-Host CNN on New Year's Eve
Cohen and Cooper will also likely be one of the few, if not the first, openly gay pair to co-host a New Year's Eve show. He exec-produced several of her stand-up specials that premiered on the NBCUniversal cabler in the early 2000s.
NBC News noted that Nielsen was a "key player" in Trump's travel ban and restrictions on immigration.
Before her time in the private sector, she served during the President George W. Bush administration as special assistant to the president and as senior director for prevention, preparedness and response at the White House Homeland Security Council.
Following Kelly's move, Elaine Duke was named acting secretary and has coordinated the department's efforts in the wake of three major hurricanes, the largest mass shooting in modern American history and an ongoing debate over the Deferred Action for Childhood Arrivals policy. 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.