Using data collected among Mexican-American adolescents, this paper tests a model positing an effect of ethnic consciousness on system blame, and an effect of system blame on political leftism. For the sample as a whole, results support the model, although the effect of system blame on leftism is weak. Further analysis reveals an interactive relationship such that system blame has a significant effect on leftism among respondents whose father's occupation is not low (nonmarginals), but no effect among respondents whose father's occupation is low (marginals). The interaction is apparently due to a greater relevance of system blame items to nonmarginal respondents.