The concept of public opinion is central to political discussion, to political action, and to virtually all ideas about the meaning of democracy and the meaning of political oppression and tyranny. Social change varies crucially both with what particular groups believe about public issues and with what the public perceives as change. Yet “public opinion” is an exceptionally ambiguous and volatile term and idea. And it is readily subject to mistaken beliefs about its current or past content. People with conflicting political aspirations rarely agree on what “public opinion” is at any particular time and place, and each group's perception is likely to support its own policy preferences. Because there is no one “public” but rather many different ones that change constantly, this multiplicity of perceptions of public opinion is inevitable.

Nor is there any objective way to ascertain what public opinion is for any group of people or to define it accurately. Social scientists often rely on survey research to do so, and journalists conduct and cite polls of opinion. But the conclusions of surveys and polls depend crucially on what questions are asked and what news events respondents have in mind when they answer. George Bush's popularity was very high just after the conclusion of the Gulf War of 1991–1992 when the Pentagon and White House version of alleged victory in that war was generally accepted; but Bush's popularity plummeted just a few months later when the war was largely forgotten and people focused to a much greater extent on the serious problems of the economy.