John R. Bolton
In April 2018, John R. Bolton was appointed National Security Advisor for President Donald Trump. Fleitz had previously served as Bolton's Chief of Staff at the State Department during the Presidency of George W. Bush. Bolton selected Fleitz to serve as his NSC Chief of Staff, replacing Keith Kellogg. He left his position on October 31 of that year to rejoin the Center for Security Policy and was succeeded by Joan Virginia O’Hara.