President Donald Trump said Friday that Stephen Miller will replace Susie Wiles as White House chief of staff, with the change taking effect Monday, November 9. Miller is currently the deputy chief of staff for policy and one of Trump’s longest-serving advisers.

Trump said Wiles would move to work with his political organization. The Associated Press reported that Wiles gave Trump her resignation on Thursday, citing a person familiar with the conversation. Reuters also reported the planned transition and its Monday start date.

Miller has been a central figure in shaping the administration’s immigration policy. His move to the chief of staff position places a close policy adviser in the role coordinating White House operations and access to the president. Wiles, the first woman to serve as Trump’s chief of staff, had held the job since the start of his current term.

The announcement comes days after Republicans lost control of Congress in the midterm elections. Trump has not publicly detailed how responsibilities will be divided between Miller’s new role and Wiles’s work with his political operation.

Sources: Associated Press; Reuters.