Miller ran unsuccessfully for lieutenant governor in 1950,[1] losing his bid for the nomination as running mate to gubernatorial nominee James Roosevelt.

Together with U.S. Senate nominee Helen Gahagan Douglas, Roosevelt was deserted by the old-line state Democratic organization of San Francisco boss William M. Malone, with the acquiescence of President Harry S. Truman and other Washington, D.C.

Roosevelt and Douglas at first encouraged and supported him for the position, but then double-crossed Miller, who was opposed by Malone, and instead chose a little-known man from the San Joaquin Valley.

Brown's campaign manager and political strategist, Don Bradley, was an old and close friend of Miller, whom he called "the best politician I ever ran into", and they worked closely together to "engineer" the election of more liberal Democrats to the state Senate; their unsung efforts "changed the ideological complexion" of the conservative upper house, and thus "made possible the enactment of much of the Democratic legislation" of the Brown years.

[5] Miller died in office unexpectedly, six days before his 55th birthday, two years after Governor Brown was defeated for re-election by Ronald Reagan.