Public opinion can be defined as those opinions held by ordinary citizens which government takes into account in making its decisions. Public officials have many ways of assessing public opinion, such as the outcomes of elections, but have increasingly come to rely on public opinion polls. There are many possible sources of error in polls, and surveys sometimes present a misleading image of the public's views. However, a properly conducted poll can provide an accurate indication of what the public is thinking and can dissuade political leaders from thinking that the views of the most vocal citizens (such as demonstrators and letter writers) are also the views of the broader public.
The process by which individuals acquire their political opinions is called political socialization. During childhood the family and schools are important sources of basic political attitudes, such as beliefs about the parties and the nature of the U.S. political and economic systems. Many of the basic orientations that Americans acquire during childhood remain with them in adulthood, but socialization is a continuing process. Major shifts in opinion during adulthood are usually the consequence of changing political conditions; for example, the Great Depression of the 1930s was a catalyst for wholesale changes in Americans' opinions on the government's economic role. There are also short-term fluctuations in opinion that result from new political issues, problems and events. Individuals' opinions in these cases are affected by prior beliefs, peers, political leaders and the news media. Events themselves are also a significant short-term influence on opinions.
The frames of reference that guide Americans' opinions include cultural beliefs, such as individualism, which result in a range of acceptable and unacceptable policy alternatives. Opinions can also stem from ideology, although most citizens do not have a strong and consistent ideological attachment. In addition, individuals develop opinions as a result of group orientations, notably religion, income, occupation, region, race, gender or age. Partisanship is perhaps the major source of political opinions; Republicans and Democrats differ in their voting behavior and views on many policy issues. However, party loyalty has declined in importance in recent decades as a frame of reference for people's opinions.
Public opinion has a significant influence on government but seldom determines exactly what government will do in a particular instance. Public opinion constrains the policy choices of officials. Some policy actions are beyond the range of possibility because the public will not accept change in existing policy or will not seriously consider policy that seems clearly at odds with basic American values. Evidence indicates that officials are reasonably attentive to public opinion on highly visible and controversial issues of public policy.