Sullivan was close with former Secretary of State Clinton, working on the former first lady's 2008 presidential campaign as a top adviser. At the State Department, he replaced Anne-Marie Slaughter as the Director of Policy Planning after she returned to Princeton University.

Sullivan also worked as an adviser to Sen. Amy KlobucharAmy Jean KlobucharTrump quietly putting his stamp on the courts CNN's Zeleny: Leaderless Democrats 'in complete disrepair and disarray' Lacking White House plan, Senate focuses on infrastructure MORE (D-Minn.) and is a graduate of Yale and Oxford.