The “Two-Step-Flow Hypothesis” presented here results from the often-referenced election campaign study with the project title “The People’s Choice. How the Voter Makes Up His Mind in a Presidential Campaign.” Lazarsfeld, Berelson and Gaudet (The people’s choice: how the voter makes up his mind in a presidential campaign, 3rd ed. Columbia University Press, New York, 1948 and 1968) examined during the 1940 presidential election in the USA, Lazarsfeld, together with Berelson and Gaudet, investigated the impact of radio and press on the political opinion formation of voters. The surprising result of their empirical panel study was that voters were more influenced in their political decisions by face-to-face contacts with other people in their immediate environment than by the media campaigns and media reports. Not only was the potential influence of direct and short-term media exposure significantly lower than that of social contacts in the immediate environment, but voters also selectively exposed themselves to media and communicators that supported their existing attitudes and beliefs. This reinforcement effect was attributed to the political homogeneity of the groups to which the respondents belonged and in which the voters were anchored with their attitudes.