Public opinion is an incredibly hard thing to analyze, and neither historians nor social and political scientists have really got to grips with it. Just about all politicians claim that what they're doing is in line with public opinion, or else they claim (often the case with foreign policy) that the public doesn't know what's good for them and should listen to their 'leadership'.
Access to polling data makes us less likely to straightforwardly characterize a period of history or a contemporary situation with a particular label, such as 'imperialist' or 'liberal'. The existence of poll data makes the application of labels unsatisfactory. However, the fact we are aware of this situation may seem like an unhappy circumstance because simply arranging the poll data that creates this complexity apparently also sheds little light on overall 'public opinion' in a period.
Take this is an example. If you were to look at American foreign policy at the moment, you would rightly conclude it was aggressive and active; this is not an age of isolationism. This general tone of policy was very popular in the aftermath of the terrorist attacks, and understandably so. However, since then, particular policies of the American government have alienated segments of the American public, such that there is no longer a consensus. Should we then describe American public opinion as currently aggressive and pro-active in foreign policy?
Certainly part of it is, but then we also know that a large part isn't. Those of us with our eyes open know that Noam Chomsky is wrong and that dissent is strongly reflected in the media (let's not argue about how strongly, but let's not deny it exists), in cultural products such as books and theatre, and in voting patterns. Clearly the actions of the American government aren't a clear guide to the feelings of the American people (it may be sometimes and not at others). Opponents of America acknowledge this all the time: they say they're opposed to the American government, but they extend a warm hand to the American people. And such can be true of any people and their government.
This raises all sorts of questions. Can we ever know 'public opinion'? Does it even exist as a discrete, measurable entity? And why should we care?
First, a historical point. Historians are often too eager to label a particular period as 'isolationist' or 'imperialist', or to condemn a particular people for the actions of their government. But the truth is, we really don't understand the relationship between public opinion and policy-making even in contemporary situations: how on earth can we hope to understand it in times way gone past? Before the 1940s we can't even line up poll data.
It seems to me more reasonble, then, to think about the relationship today, rather than fifty or one hundred years ago. We can try and understand public opinion today by all the sources I mentioned above, and by the people we encounter in our environment. The policy maker also has access to the same sources. Yet, if you think about it, we can never know more than a fraction of the truth about it. People read articles in publications they agree with, and they tend to remember poll data that fits with their views rather than the contrary, and they go along their lives. Even an honest investigation of the thing would never yield more than partial results.
How can something so fragmentory and contradictory be useful? Well, people make it useful because it's malleable. In the absence of 80% showings in the polls consistently against their point of view, pretty much any evidence can be interpreted favourably. All members of the government and legislators claim they're acting in the name of Public Opinion, whether they're fulfilling an electoral mandate or pursuing the national interest in ways that might actually be specifically opposed by the public. Public opinion's ability to throw up points of view contradictory to the national interest is especially irksome to the foreign policy maker, who likes to claim they just don't know what's good for them.
And in general this works just fine. Most people are apathetic and disinterested in issues, and go about their daily lives scarcely aware hundreds of officials are invoking their desires as justification for a new tax on knickers or the invasion of another country. The interested minority sometimes have difficulty getting their voices heard, but have a number of tools at their disposal: the letter to the editor, the protest march, and the vote. Yet it is not clear exactly how any of these impact on the policymaker.
Policymakers and bureaucracies, especially ones that aren't very good, tend to keep on doing what they're doing until they have good reason to do otherwise. An overwhelming outpouring of dissent will probably make them change their mind for reasons of conscience and bacon-saving. This is the main effect public opinion can have: in opposition. You rarely get protest marches of millions advocating that something new and pro-active be done, but you get plenty of protests about this or that thing. That's why it's called a protest and its partner is called dissent. You protest at something and you dissent from something.
However, protest and dissent can be confusing phenomenon in themselves. They can often come from vocal minorities. These people tend to be really pissed off and they don't give up easily: the New Left in the United States in the 1960s, for instance, or animal rights protestors today. Nixon's Silent Majority actually existed: it voted him into office and supported his actions. And so, we have to be careful of the claims of oppositional groups to represent 'public opinion' just as much as we do the claims of the officials.
Let's let the political scientists continue to have their arguments on the subject. You might well ask why any of this matters. Well, it matters because of this. Peace can only be furthered by an understanding between peoples that they share a fundamental humanity. Governments often act in a way that doesn't appear particularly human, and we make a mistake if we characterize all members of a nation due to the actions of the state that rules over them. We don't even understand how the opinions and ideas of citizens in Western democracies are filtered to the politicians and policymakers. Let's not go judging the people of parts of the world where political apathy is not a luxury of bourgeois wealth, but a necessity of life and death.