Can biased polls distort electoral results? Evidence from the lab

Abstract

We introduce a new methodological approach for studying the effect of biased polls on election outcomes and apply it to a set of new experiments with 375 participants. Voters may observe and learn about the bias by playing multiple voting rounds. While in control conditions, polls are unbiased, in treatment conditions, participants view only poll results where a particular candidate’s vote share is the largest. This candidate is consistently elected more often in the treatments than in the controls, because biased polls robustly distort voters’ expectations about vote shares. This effect holds after eighteen election rounds, out of which the first three are practice rounds, but somewhat more weakly in our main treatment where voters are explicitly informed about the bias.