In this year of American Presidential election, I noticed that many political analyst referred a book by political scientist Samuel L Popkin, The Reasoning Voter. One of his point is that voters are not completely irrational, but rather behave as decision-makers under certainty. They use "low-information signals" such as appearances, character traits or "whether you know how to roll a bowling ball or wear an American-flag pin" (from Time's Joe Klein column). In other words, political heuristics.
Here is a more detailed summary from Wikisummary.
Low information rationality
Popkin's analysis is based on one main premise: voters use low information rationality gained in their daily lives, through the media and through personal interactions, to evaluate candidates and facilitate electoral choices.
Political "Knowledge": Despite a more educated electorate, knowledge of civics has not increased significantly in forty years. According to Popkin, theorists who argue that political competence could be measured by knowledge of "civics book" knowledge and names of specific bills (i.e. the Michigan studies) have missed the larger point that voters do manage to gain an understanding of where candidates stand on important issues. He argues that education has not changed how people think, but it does allow us to better interpret and connect different cues.
Information as a By-Product: Popkin argues that most of the information voters learn about politics is picked up as a by-product of activities they pursue as a part of daily life (homeowners learn about interest rates, shoppers learn about prices and inflation etc.--thus, people know how the economy is doing). Media helps to explain what politicians are doing and the relevance of those actions for individuals, and campaigns help to clarify the issues. Voters develop affinity towards like-minded opinion leaders in media and in personal interactions.
Media and Friends: Interpersonal communication is seen as a way of developing assessments of parties and candidates. Information received from the media is discussed with friends and helps to create opinions. While voters do care about issue proximity, they also focus on candidate competency and sincerity and rely heavily on cues to make these evaluations.
Other related post:A Neuropolitic look at political psychology