The document discusses the two-step flow model of communication, which hypothesizes that ideas from mass media flow first to opinion leaders and then from opinion leaders to the wider population. It was first introduced in 1944 and elaborates that most people are influenced indirectly through opinion leaders who are exposed to media messages and interpret them based on their own opinions before spreading them to others. Opinion leaders tend to be similar demographically or socially to those they influence. The two-step model provides an explanation for why some media campaigns do not change attitudes at a wide scale.