Jonathan Mummolo

Tea Party Influence: A Story of Activists and Elites

Understanding how the Tea Party has affected congressional elections and roll call voting helps us understand not only an important political movement, but how movements affect politics more generally. We investigate four channels for the movement to influence political outcomes: activists, constituent opinion, group endorsement activity and elite-level self-identification. We find consistent evidence that activists mattered both electorally and for roll call voting on issues of importance to the movement. Constituent opinion had virtually no impact on either political outcome. Group endorsement activity had possible effects on elections, but mostly no effect on congressional voting. Self-identification among elites did not enhance—or harm—Republican electoral fortunes, but did affect congressional votes important to the movement. These divergent results illustrate how movement politics can influence outcomes through multiple channels and call into question the usefulness of the “Tea Party’’ moniker without important qualifiers.

Why Partisans Do Not Sort: The Constraints on Political Segregation

Social divisions between American partisans are growing, with Republicans and Democrats exhibiting homophily in a range of seemingly nonpolitical domains. It has been widely claimed that this partisan social divide extends to Americans’ decisions about where to live. In two original survey experiments, we confirm that Democrats are, in fact, more likely than Republicans to prefer living in more Democratic, dense, and racially diverse places. However, improving on previous studies, we test respondents’ stated preferences against their actual moving behavior. While partisans differ in their residential preferences, on average they are not migrating to more politically distinct communities. Using zip-code-level census and partisanship data on the places where respondents live, we provide one explanation for this contradiction: by prioritizing common concerns when deciding where to live, Americans forgo the opportunity to move to more politically compatible communities.

News from the Other Side: How Topic Relevance Limits the Prevalence of Partisan Selective Exposure

Prior research has demonstrated a preference among partisans for like-minded news outlets, a key mechanism through which the media may be polarizing Americans. But in order for source reputations to cause widespread selective exposure, individuals must prioritize them above other competing attributes of news content. Evaluating the relative influence of various contributors to media choice is therefore critical. This study pits two such factors, source reputation and topic relevance, against one another in conjoint survey experiments offering randomly paired news items to partisans. Making a news source’s reputation politically unfriendly lowers the probability that an individual chooses an item, but this negative effect is often eclipsed by the positive effect of making a news topic relevant to the individual. In many popular modern news consumption environments, where consumers encounter a diverse mixture of sources and topics, the ability of source reputations to contribute to polarization via partisan selective exposure is limited.

Modern Police Tactics, Police-Citizen Interactions, and the Prospects for Reform

High-profile incidents of police misconduct have led to widespread calls for law enforcement reform. But prior studies cast doubt on whether police commanders can control officers, and offer few policy remedies because of their focus on potentially immutable officer traits like personality. I advance an alternative, institutional perspective and demonstrate that police officers—sometimes characterized as autonomous—are highly responsive to managerial directives. Using millions of records of police-citizen interactions alongside officer interviews, I evaluate the impact of a change to the protocol for stopping criminal suspects on police performance. An interrupted time series analysis shows the directive produced an immediate increase in the rate of stops producing evidence of the suspected crime. Interviewed officers said the order signaled increased managerial scrutiny, leading them to adopt more conservative tactics. Procedural changes can quickly and dramatically alter officer behavior, suggesting a reform strategy sometimes forestalled by psychological and personality-driven accounts of police reform.

Militarization fails to enhance police safety or reduce crime but may harm police reputation

Significance National debates over heavy-handed police tactics, including so-called “militarized” policing, are often framed as a trade-off between civil liberties and public safety, but the costs and benefits of controversial police practices remain unclear due to data limitations. Using an array of administrative data sources and original experiments I show that militarized “special weapons and tactics” (SWAT) teams are more often deployed in communities of color, and—contrary to claims by police administrators—provide no detectable benefits in terms of officer safety or violent crime reduction, on average. However, survey experiments suggest that seeing militarized police in news reports erodes opinion toward law enforcement. Taken together, these findings suggest that curtailing militarized policing may be in the interest of both police and citizens. The increasingly visible presence of heavily armed police units in American communities has stoked widespread concern over the militarization of local law enforcement. Advocates claim militarized policing protects officers and deters violent crime, while critics allege these tactics are targeted at racial minorities and erode trust in law enforcement. Using a rare geocoded census of SWAT team deployments from Maryland, I show that militarized police units are more often deployed in communities with large shares of African American residents, even after controlling for local crime rates. Further, using nationwide panel data on local police militarization, I demonstrate that militarized policing fails to enhance officer safety or reduce local crime. Finally, using survey experiments—one of which includes a large oversample of African American respondents—I show that seeing militarized police in news reports may diminish police reputation in the mass public. In the case of militarized policing, the results suggest that the often-cited trade-off between public safety and civil liberties is a false choice.

How Content Preferences Limit the Reach of Voting Aids

Voters are often uninformed about the political candidates they choose between. Governments, media outlets, and civic organizations devote substantial resources to correcting these knowledge deficits by creating tools to provide candidate information to voters. Despite the widespread production of these aids, it remains unclear who they reach. We collect validated measures of online voter guide use for more than 40,000 newspaper readers during a state primary election. We show this newspaper-produced voter guide was primarily used by individuals with high levels of political interest and knowledge, a finding in contrast to earlier hypotheses that providing guides directly to voters online would reduce disparities in use based on political interest. A field experiment promoting the voter guide failed to diminish these consumption gaps. These results show that the same content preferences that contribute to an unequal distribution of political knowledge also impede the effectiveness of subsequent efforts to close knowledge gaps.

Obstacles to Estimating Voter ID Laws’ Effect on Turnout

Widespread concern that voter identification laws suppress turnout among racial and ethnic minorities has made empirical evaluations of these laws crucial. But problems with administrative records and survey data impede such evaluations. We replicate and extend Hajnal, Lajevardi, and Nielson’s 2017 article, which concludes that voter ID laws decrease turnout among minorities, using validated turnout data from five national surveys conducted between 2006 and 2014. We show that the results of their article are a product of data inaccuracies, the presented evidence does not support the stated conclusion, and alternative model specifications produce highly variable results. When errors are corrected, one can recover positive, negative, or null estimates of the effect of voter ID laws on turnout, precluding firm conclusions. We highlight more general problems with available data for research on election administration, and we identify more appropriate data sources for research on state voting laws’ effects.

Evaluating the Substantive Significance of Linear Fixed Effects Regression Results

The counterfactuals researchers commonly use to assess the substantive significance of linear fixed effects regression results do not account for the manner in which these models are estimated. Importantly, including fixed effects in a regression means that the model is estimated based on the often narrow within-unit distribution of an independent variable. Despite this, counterfactuals are often motivated with features of an independent variables overall distribution (e.g., its range or standard deviation). Using simulated data and two case studies, we show this approach has two consequences. First, it inflates the substantive significance of any variables assessed in this way. Second, these counterfactuals are unreliable and exhibit a high degree of model dependence. We recommend instead that researchers assess the substantive significance of fixed effects regression results with counterfactuals based on the within-unit distribution of an independent variable. We provide an R function to implement this recommendation.