Cook briefly served as the acting attorney general of Massachusetts on January 5, 2023, for a few hours in the morning after Maura Healey resigned to become Governor of Massachusetts but before her swearing in at noon. She resigned at noon to become Healey's chief of staff. State Solicitor Bessie Dewar then served as the acting attorney general of Massachusetts, taking the helm of the Massachusetts Attorney General's Office from Cook, from noon on January 5, 2023 until Attorney General Andrea Campbell was sworn in on January 18, 2023. Then Attorney General-elect Campbell named Pat Moore to succeed Cook as First Assistant Attorney General.
