Researchers examine the surprising rise of affective polarization among American partisans. Using implicit, explicit, and behavioral measures, they demonstrate how negative feelings toward opposing parties have become ingrained.

Implicit & Explicit Bias Measures:

* Implicit (automatic) hostility toward the out-party is common in voters' minds.

* Affective polarization based on party is nearly as strong as racial polarization.

Behavioral Consequences:

* Partisans show discrimination against opposing partisans, sometimes exceeding racial divides.

* This animosity increases because norms against openly expressing negative sentiment are weak.

The findings suggest that partisan feelings shape political behavior in powerful ways.