Bradley effect

The tendency for polls to overestimate support for a white candidate running against a Black candidate. It is often attributed to respondents giving socially desirable answers rather than expressing their voting intentions.

Social desirability bias: The tendency to give answers that seem socially acceptable rather than accurately reporting one's beliefs or behavior. It is the leading explanation for why respondents may overstate support for a Black candidate's opponent.
Tom Bradley: An American politician who served as mayor of Los Angeles from 1973 to 1993 and ran for California governor in 1982. The effect was named after Bradley following his unexpected loss in the 1982 governor's race.
Opinion poll: A survey that estimates the views or intended choices of a population at a particular time. The effect concerns discrepancies between pre-election poll estimates and eventual vote totals.
Ecological fallacy: The error of inferring individual behavior from patterns observed in groups. Aggregate poll errors cannot by themselves establish that individual respondents concealed their preferences.
Nonresponse bias: Bias that occurs when people who do not respond to a survey differ systematically from those who do. Polls can miss voters whose preferences differ from those of people willing to answer.
1982 California gubernatorial election: The election in which Republican George Deukmejian defeated incumbent Los Angeles mayor Tom Bradley for California governor. Pre-election polls showed Bradley ahead, while the result gave rise to the effect's name.
Election forecasting: The practice of estimating election outcomes from polls, historical data, and other evidence. Forecasters must decide whether a proposed Bradley effect warrants adjusting candidate support estimates.
List experiment: A survey technique that estimates sensitive views by comparing counts across randomized lists of statements. It can estimate socially sensitive attitudes without asking respondents to disclose them directly.
Sampling bias: Systematic error caused by selecting a sample that does not represent the population being studied. A poll's racial and political composition can distort its estimate independently of dishonest answers.
George Deukmejian: A Republican politician who served as governor of California from 1983 to 1991. His 1982 victory over Bradley became the result that the effect was meant to explain.

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2016 United States presidential electionCompared with: It was invoked to explain polling error, though evidence does not establish it as the cause of 2016 misses.