"We also learned an important lesson from Sinclair's campaign. Sinclair had been a socialist ever since the Debs era. He had run for office on the Socialist ticket many times without much success. In 1934, to the dismay of his comrades in the Socialist Party, and to our contempt, he decided to run for the Democratic nomination for governor in California. He put together a ticket called End Poverty in California, or EPIC, which took as its slogan "production for use, not profit," and advocated state-sponsored cooperative enterprises. The EPIC movement swept the Democratic Party, gained Sinclair the Democratic nomination (if not, ultimately, the governorship), and roused enormous popular enthusiasm. We would have nothing to do with the Democratic Party, and so we were left on the outside, denouncing the movement. We called him a "social fascist," which was terrible nonsense. (Lest it be thought that such sectarianism was solely a CP attribute, it's worth remembering that the Socialist Party expelled Sinclair for his act of heresy.) Our position was that you could not reform a capitalist party, that nothing could be gained through the two-party system."
January 1, 1970
https://en.wikiquote.org/wiki/Upton_Sinclair