In October 1946 David Lilienthal asked Bacher to become one of the inaugural commissioners of the United States Atomic Energy Commission, the civilian agency that was being formed to replace the wartime Manhattan Project. As a Republican, Bacher was easily confirmed by the Senate members of the United States Congress Joint Committee on Atomic Energy by an 8–0 vote. As he was the only one of the five commissioners who was a scientist—an important factor in his decision to accept the post—he played a leading role in the selection of the Atomic Energy Commission's influential General Advisory Committee to which nine scientists were appointed: James Conant, Lee DuBridge, Enrico Fermi, Robert Oppenheimer, Isidor Isaac Rabi, Hartley Rowe, Glenn Seaborg, Cyril Stanley Smith and Hood Worthington.