Public opinion is characterized, on the one hand, by its form as elementary collective behavior (Blumer 1972) and, on the other, by its functions as a means of social control (Ross 1901). It comes into play in situations that are problematical or normatively ambiguous in one or more of several senses: The situation is novel and unprecedented, so that established ways of coping no longer prove adequate, people actively disagree over which of several conventionally acceptable practices should apply, or the conventions themselves have come under serious challenge by a dissident group. In the extreme case, controversy over what should be done can heat up to a point where order gives way to violent group conflict.

Interest in public opinion is historically linked to the rise of popular government. Although rulers have always had to display some minimum sensitivity to the needs and demands of their subjects, they...