Depending on elegant question-design and measurement, the study of public opinion in the Bureau of Applied Social Research (BASR) had produced substantial knowledge about the relation between communications and formation of public opinion, but such study only gained the precision of detail, failing to achieve the generality and certainty of knowledge as the researchers committed to. This paper scrutinizes Voting which had the most skillful measurement in BASR, to identify the relation between methodological individualism, ideas of public opinion and communication under the S-R theory, and the model of knowledge-producing. The author takes the predicament of knowledge-producing as a self-fulfilling prophecy through methodology used.