During every presidential election, questions arise over the results of political polls and how those surveys are conducted. This year's hot topic is the partisan composition of the leading national polls. Politicians and pundits alike now scrutinize a survey sample's partisan split as closely as the horse-race results. Surveys that are deemed to have “too many” Republican or Democratic respondents are widely viewed as biased in favor of George Bush or John Kerry.
These assertions reflect fundamental misunderstanding of party affiliation and how it is measured by polling organizations. Party affiliation is derived from a question typically found at the end of a survey questionnaire, in which respondents are asked how they regard themselves in politics at the moment. In Pew Research Center surveys, the question asks: “In politics today, do you consider yourself a Republican, Democrat or Independent?”
This question is not intended to measure how respondents are registered, how they have voted in the past, or how they have thought of themselves throughout most of their lives. Like most other questions on public opinion surveys, it is intended to measure current feelings about politics – in this case, their feelings of affiliation or disaffection with the major political parties.
Given that it is an attitude and not a personal characteristic, it is not at all comparable to race, ethnicity, gender, age, education, or other demographic markers that are routinely used to check on the representativeness of surveys. Further, long-term tracking and analysis of party identification finds that, for a number of reasons, it varies a good deal from survey to survey.