LAUSR

Significance Political polarization increasingly threatens democratic institutions. The belief that “my side” sees the world objectively while the “other side” sees it through the lens of its biases contributes to this political polarization and accompanying animus and distrust. This conviction, known as the “objectivity illusion,” was strong and persistent among Trump and Clinton supporters in the weeks before the 2016 presidential election. We show that the objectivity illusion predicts subsequent bias and polarization, including heightened partisanship over the presidential debates. A follow-up study showed that both groups impugned the objectivity of a putative blog author supporting the opposition candidate and saw supporters of that opposing candidate as evil. Two studies conducted during the 2016 presidential campaign examined the dynamics of the objectivity illusion, the belief that the views of “my side” are objective while the views of the opposing side are the product of bias. In the first, a three-stage longitudinal study spanning the presidential debates, supporters of the two candidates exhibited a large and generally symmetrical tendency to rate supporters of the candidate they personally favored as more influenced by appropriate (i.e., “normative”) considerations, and less influenced by various sources of bias than supporters of the opposing candidate. This study broke new ground by demonstrating that the degree to which partisans displayed the objectivity illusion predicted subsequent bias in their perception of debate performance and polarization in their political attitudes over time, as well as closed-mindedness and antipathy toward political adversaries. These associations, furthermore, remained significant even after controlling for baseline levels of partisanship. A second study conducted 2 d before the election showed similar perceptions of objectivity versus bias in ratings of blog authors favoring the candidate participants personally supported or opposed. These ratings were again associated with polarization and, additionally, with the willingness to characterize supporters of the opposing candidate as evil and likely to commit acts of terrorism. At a time of particular political division and distrust in America, these findings point to the exacerbating role played by the illusion of objectivity.