This thesis attempts to ascertain whether Upton Sinclair's Democratic nomination for governor of California in 1934 caused the resurgence of the Democratic Party in California, or whether his nomination was a product of that party's resurgence between 1928 and 1942. Given Sinclair's decision on the unsuitability of the Socialist Party, were his judgments that: (1) the Democratic Party was in resurgence and, (2) it was moving to the left, sound ones? To make these determinations the thesis investigates why Sinclair rushed to capture the Democratic nomination, exploring his methods and techniques and those used to defeat him. It also examines the reactions of the Democratic Party leaders of the right and left wings toward the Sinclair candidacy, and analyzes the primary and general.election returns -- citing differences and similarities between Northern and Southern California -- which predicate that Sinclair's decision was: (I) based on faulty judgement, and (2) based on an inaccurate appraisal of the position of the Democratic Party.