Public opinion is the collective attitude of citizens on a given issue or question.
Citizens have collected attitudes (ideologies) concerning a given issue or question. Also, citizens are willing to register opinions on matters outside their expertise. Opinions are imperfect indicators of an underlying and unobserved attitude. An attitude is an enduring predisposition to respond in a positive or negative way about a person, object or issue. This predisposition lasts a long time but is capable of changing. For example, liberalism, conservatism and socialism are examples of predispositions. In addition -- and more arbitrarily -- somebody bit by a dog might be predisposed against dogs. To determine the public's predispositions, it is crucial to recognize what is the public. It can be the adult population, Republican population and nearly any other demographic imaginable -- and any combination thereof.
Public opinion has the following characteristics:
The public's attitudes toward a given government policy can vary over time, often dramatically.
Public opinion places boundaries on allowable types of public policy.
If asked by pollsters, citizens are willing to register opinions on matters outside their expertise.
Governments tend to respond to public opinion.
The government sometimes does not do what the people want.
There are three views on the nature of public opinion:
Traditional View (Democratic Theorists): most voters have stable preferences about most issues; politicians tap into this and make decisions based on public opinion.
Revised View (Phil Converse): most voters have non-opinions. Converse found that slightly changing wording inconsequentially changes opinions dramatically. Also, Converse found that graphs paralleled those when coins are flipped.
Current View (John Zaller): most voters possess positive and negative feelings about the same object (ambivalence).
The two primary theories to consider are: Phil Converse's Response Instability theory and John Zaller's Memory-Based Information Processing theory.
Regarding Phil Converse's Response Instability theory, Converse himself stated, "Large portions of electorate simply do not have meaningful beliefs, even on issues that have formed the basis for intense political controversy among elites for substantial periods of time." According to this, people have feelings but lack attitudes. People have response instability and their responses seem random. Thus, opinions of a large segment of the population are a matter of chance.
Regarding John Zaller's Memory-Based Information Processing theory, Zaller contended that people possess conflicting considerations about the same issue. A consideration is anything stored in memory that might affect the outcome of responding one way or another. People do not conduct exhaustive research into their memory when responding to polls, so whatever is at the "top of their mind" is defined by a myriad of random daily factors.
When responding to survey questions, individuals do not conduct an exhaustive search of their considerations, and do sample those considerations at the top of their head. When retrieving information from memory, some is inaccessible (I just can't remember your name) and some is very accessible (it's on my mind).
There are two kinds of people: univalent persons and ambivalent people. Univalents' considerations are stable over time, and when univalents encounter information that challenges their existing views they counter-argue. Their attitudes are consistent and they have consistent opinions. Ambivalent people have inconsistent considerations and accept all information indiscriminately. The considerations in the back of their head are all mixed, so the considerations on the top of their head are unpredictable. Thus, ambivalent persons express unstable opinions.