  Extreme polarization can undermine democracy by making compromise impossible
and transforming politics into a zero-sum game. Ideological polarization - the
extent to which political views are widely dispersed - is already strong among
elites, but less so among the general public (McCarty, 2019, p. 50-68). Strong
mutual distrust and hostility between Democrats and Republicans in the U.S.,
combined with the elites' already strong ideological polarization, could lead
to increasing ideological polarization among the public. The paper addresses
two questions: (1) Is there a level of ideological polarization above which
polarization feeds upon itself to become a runaway process? (2) If so, what
policy interventions could prevent such a dangerous feedback loop? To explore
these questions, we present an agent-based model of ideological polarization
that differentiates between the tendency for two actors to interact (exposure)
and how they respond when interactions occur, positing that interaction between
similar actors reduces their difference while interaction between dissimilar
actors increases their difference. Our analysis explores the effects on
polarization from different levels of tolerance to other views, responsiveness
to other views, exposure to dissimilar actors, multiple ideological dimensions,
economic self-interest, and external shocks. The results suggest strategies for
preventing, or at least slowing, the development of extreme polarization.
