=+31. Bradley effect. The Bradley effect theory posits that inaccurate polls are skewed by the phenomenon of voters giving inaccurate polling responses because they fear that, by stating their true preference, they will open themselves to criticism of racial or ethnic motivation. Members of the public may feel under pressure to provide an answer that is deemed to be more publicly acceptable, or ‘politically correct’, but they vote according to their true preference. Is the Bradley effect an example of bias, or of sampling error?