In 1952, Miller was one of the few California Democratic office-holders among the early supporters of the presidential campaign of Senator Estes Kefauver of Tennessee. The regular party organization had originally supported the re-election of President Truman, but when Truman withdrew from the race, the party professionals, in desperation, coalesced around Pat Brown as a "favorite son." In the June primary, Kefauver easily defeated the Brown slate and the winning California delegation to the Democratic National Convention, largely composed of Kefauver supporters, chose Miller as delegation chairman. Kefauver later lost the nomination to Illinois Governor Adlai Stevenson, a late entry into the race, but that fall, both the Truman professionals and the Kefauver and Stevenson amateurs at last united in selecting Miller as the new chairman of the state Democratic Party. He held this post for two years.