In the 1970s, political scientist Richard Fenno followed members of Congress on tours around their districts. Fenno observed how they interacted with voters so that he could study how politicians perceive their constituents and how these perceptions guide their behavior. As Fenno noticed, politicians have intuitions about which voters are supporters and which are opponents, what issues voters care about, and how the politicians ought to present themselves to the diverse audiences they encounter across their districts. But perceptions like these can be vague and distorted. Distorted as they may be, these perceptions guide politicians in their efforts to represent the public.

In contemporary politics, perceptions of voters are not merely vague ideas carried around in the heads of politicians; perceptions are also recorded in detailed electronic profiles that describe each constituent within a jurisdiction. As is now well known, political parties in recentyears have built databases to facilitate targeting strategies. These databases list the names and contact information for all voters in a district, along with information about their personal traits, their neighborhoods, and their history of political participation. Politicians and their campaigns use these lists to perceive the electorate. The lists help them understand who their supporters are, what issues different voters care about, and how they should present themselves to voters in their campaign appeals.