Just 30 minutes from San Francisco sits the city of Richmond, Calif., which has quietly become one of the country’s most unusual political experiments. It’s a city where an activist coalition that includes democratic socialists has exercised influence over local government for years. From the outside, Richmond looks like any other  working-class California city  with a massive Chevron refinery looming over the shoreline and immigrant-owned businesses lining 23rd Street. Politically, however,