Regan, Donald Thomas (rēˈgən) [key], 1918–2003, U.S. government official and financier, b. Cambridge, Mass. A graduate of Harvard (B.A. 1940), he went to work (1946) at a brokerage house that became Merrill Lynch after serving as a Marine officer in World War II. Regan rose through the company to become its youngest president in 1968 and chief executive in 1973, transforming the firm into a publicly owned financial services company. A long-time Republican, he was active in Ronald Reagan's presidential campaign and became (1981) his Treasury secretary and a strong advocate of supply-side economics, tax cuts, government cutbacks, and deregulation. In 1985 he became White House chief of staff, a post in which he wielded great power. As revelations concerning the Iran-contra affair hurt the president's image, the first lady blamed Regan and worked to force him out. Regan resigned in 1987 and wrote For the Record (1988), in which he attacked Nancy Reagan; she shot back in My Turn (1989).