As The Unpolitical Animal explains, political scientist Philip Converse examined beliefs and voting behavior forty years ago in an article called “The Nature of Belief Systems in Mass Publics”:
Converse claimed that only around ten per cent of the public has what can be called, even generously, a political belief system. He named these people “ideologues,” by which he meant not that they are fanatics but that they have a reasonable grasp of “what goes with what”—of how a set of opinions adds up to a coherent political philosophy. Non-ideologues may use terms like “liberal” and “conservative,” but Converse thought that they basically don’t know what they’re talking about, and that their beliefs are characterized by what he termed a lack of “constraint”: they can’t see how one opinion (that taxes should be lower, for example) logically ought to rule out other opinions (such as the belief that there should be more government programs). About forty-two per cent of voters, according to Converse’s interpretation of surveys of the 1956 electorate, vote on the basis not of ideology but of perceived self-interest. The rest form political preferences either from their sense of whether times are good or bad (about twenty-five per cent) or from factors that have no discernible “issue content” whatever. Converse put twenty-two per cent of the electorate in this last category. In other words, about twice as many people have no political views as have a coherent political belief system.
Some more stats:
Seventy per cent of Americans cannot name their senators or their congressman. Forty-nine per cent believe that the President has the power to suspend the Constitution. Only about thirty per cent name an issue when they explain why they voted the way they did, and only a fifth hold consistent opinions on issues over time. Rephrasing poll questions reveals that many people don?t understand the issues that they have just offered an opinion on. According to polls conducted in 1987 and 1989, for example, between twenty and twenty-five per cent of the public thinks that too little is being spent on welfare, and between sixty-three and sixty-five per cent feels that too little is being spent on assistance to the poor.