SOURCES OF POLITICIANS’ EXPRESSED AFFECTIVE POLARIZATION : IDEOLOGICAL EXTREMITY, ELECTORAL INCENTIVES, AND LEGISLATION PERFORMANCE

Politicians’ expressed affective polarization has been considered an important but less studied factor that reflects their ideology and further influences emotions in the general public. The current study has explored the changes in politicians’ expressed affective polarization level from 2011 to 2022, and examined the influence of politicians’ ideology extremity, electoral incentives, and legislative performance on their expressed affective polarization. By collecting Twitter data and applying supervised machine-learning models, the current study has depicted that politicians’ expressed affective polarization level increased rapidly in the past 12 years, much faster than the increase of ideological polarization. By analyzing the two-way fixed-effects panel data (N = 796 elites, T = 6 terms in 12 years), the current study has found that ideological extremity positively influences expressed affective polarization, while legislative performance nearly has no influence. Electoral incentives negatively impact the overall expressed affective polarization but positively impact the in-party liking expressions. However, the ideological extremity, electoral incentives, and legislative performance effect sizes are small. Meanwhile, the overall social media expression, the 2016 presidential election, and the power of control in Congress have important influences on politicians’ expressed affective polarization. The findings indicate that the media environment, political events, and politicians’ status could have a larger impact than expected. Further study directions are also discussed in the dissertation.