Dynamics of Polarizing Rhetoric in Congressional Tweetsaffective polarization is pervasive in modern us politics, and can be intensified by strategic messaging from members of Congress. But there are gaps in our knowledge of the dynamics of polarizing appeals from elected representatives on social media. We explore the usage of polarizing rhetoric by members of Congress on twitter using the 4.9 million tweets sent by members of Congress from 2009 to 2020, coded for the presence of polarizing rhetoric via a novel and highly accurate application of supervised machine learning methods. Fitting with our expectations, we find that more ideologically extreme members, those from safer districts, and those who are not in the president's party are more likely to send polarizing tweets, and that polarizing tweets garner more engagement, increasing campaign funding for more polarizing members.

Civility in political discourse is often thought to be necessary for deliberation and a healthy democracy. However, incivility is on the rise in political discourse in the United States—even from members of Congress—suggesting that political incivility may in fact be a tool to be used strategically. When and why, then, do members of Congress use incivility in their rhetoric? We develop and test expectations for the usage of political incivility by members of Congress on Twitter, using every tweet sent by a member of Congress from 2009–2020 coded for the presence of uncivil rhetoric via a novel application of transformer models for natural language processing. We find that more ideologically extreme members, those in safer electoral situations, and those who are in a position of political opposition are more likely to use incivility in their tweets, and that uncivil tweets increase engagement with members’ messages.

This paper explores the prevalence and correlates of political incivility among Congressional candidates in the 2020 election cycle, focusing specifically on which types of candidates were most likely to use uncivil language in their online communications and the self-reinforcing nature of incivility between candidates. Based on a comprehensive analysis of more than two million tweets sent by major party candidates in the 2020 House and Senate races, we conclude that several individual and electoral factors were influential in driving candidate incivility. Specifically, Republicans, challengers, and candidates in less competitive races were more likely to use uncivil rhetoric. Women, racial minorities, and candidates running in open seat races were less prone to incivility. We also find that incivility begets incivility, with candidates whose opponents used higher rates of incivility also being more likely to use incivility themselves. Uncivil tweets were also found to generate significantly more likes and retweets, suggesting that incivility is a viable means of driving engagement for candidates. These results shed light on the factors behind incivility among political elites, as well as highlight the feedback effects which contribute to a self-reinforcing rise in political incivility.

We analyze the effects of President Trump’s endorsements on House and Senate elections in 2018. Previous work has argued that presidential endorsements are usually positive or, at worst, neutral for the recipient candidates. We find that President Trump was more likely to endorse candidates with a higher pre‐endorsement likelihood of winning and to endorse candidates in more competitive races, suggesting the president used endorsements strategically both to try and help Republican candidates win and to boost his reputation for helping candidates win. However, while President Trump’s public endorsements provided a financial boost to endorsed candidates, they also increased donor support of opposing candidates and were ultimately detrimental to candidates’ vote shares and likelihood of winning. This work provides evidence for potential backlash effects among opposition voters in response to presidential endorsement in a nationalized political environment and expands our understanding of the impact of presidential campaigning in congressional midterm elections.

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