Andrew B. Hall

On the Validity of the Regression Discontinuity Design for Estimating Electoral Effects: New Evidence from over 40,000 Close Races

The regression discontinuity (RD) design is a valuable tool for identifying electoral effects, but this design is only effective when relevant actors do not have precise control over election results. Several recent papers contend that such precise control is possible in large elections, pointing out that the incumbent party is more likely to win very close elections in the United States House of Representatives in recent periods. In this article, we examine whether similar patterns occur in other electoral settings, including the U.S. House in other time periods, statewide, state legislative, and mayoral races in the U.S. and national or local elections in nine other countries. No other case exhibits this pattern. We also cast doubt on suggested explanations for incumbent success in close House races. We conclude that the assumptions behind the RD design are likely to be met in a wide variety of electoral settings and offer a set of best practices for RD researchers going forward.

Human genetic variation and the gut microbiome in disease

Taxonomic and functional changes to the composition of the gut microbiome have been implicated in multiple human diseases. Recent microbiome genome-wide association studies reveal that variants in many human genes involved in immunity and gut architecture are associated with an altered composition of the gut microbiome. Although many factors can affect the microbial organisms residing in the gut, a number of recent findings support the hypothesis that certain host genetic variants predispose an individual towards microbiome dysbiosis. This condition, in which the normal microbiome population structure is disturbed, is a key feature in disorders of metabolism and immunity.

What Happens When Extremists Win Primaries

This article studies the interplay of U.S. primary and general elections. I examine how the nomination of an extremist changes general-election outcomes and legislative behavior in the U.S. House, 1980–2010, using a regression discontinuity design in primary elections. When an extremist—as measured by primary-election campaign receipt patterns—wins a “coin-flip” election over a more moderate candidate, the party’s general-election vote share decreases on average by approximately 9–13 percentage points, and the probability that the party wins the seat decreases by 35–54 percentage points. This electoral penalty is so large that nominating the more extreme primary candidate causes the district’s subsequent roll-call representation to reverse, on average, becoming more liberal when an extreme Republican is nominated and more conservative when an extreme Democrat is nominated. Overall, the findings show how general-election voters act as a moderating filter in response to primary nominations.

The Financial Incumbency Advantage: Causes and Consequences

In this article, we use a regression discontinuity design to estimate the causal effect of incumbency on campaign contributions in the U.S. House and state legislatures. In both settings, incumbency causes approximately a 20–25 percentage-point increase in the share of donations flowing to the incumbent’s party. The effect size does not vary with legislator experience and does not appear to depend on incumbent office-holder benefits. Instead, as we show, the effect is primarily the result of donations from access-oriented interest groups, especially donors from industries under heavy regulation and those with less ideological ties. Given the role of money in elections, the findings suggest that access-oriented interest groups are an important driver of the electoral security of incumbents.

How Legislators Respond to Localized Economic Shocks: Evidence from Chinese Import Competition

We explore the effects of localized economic shocks from trade on roll-call behavior and electoral outcomes in the US House, 1990–2010. We demonstrate that economic shocks from Chinese import competition—first studied by Autor, Dorn, and Hanson—cause legislators to vote in a more protectionist direction on trade bills but cause no change in their voting on all other bills. At the same time, these shocks have no effect on the reelection rates of incumbents, the probability an incumbent faces a primary challenge, or the partisan control of the district. Though changes in economic conditions are likely to cause electoral turnover in many cases, incumbents exposed to negative economic shocks from trade appear able to fend off these effects in equilibrium by taking strategic positions on foreign-trade bills. In line with this view, we find that the effect on roll-call voting is strongest in districts where incumbents are most threatened electorally. Taken together, these results paint a picture of responsive incumbents who tailor their roll-call positions on trade bills to the economic conditions in their districts.

Assessing the External Validity of Election RD Estimates: An Investigation of the Incumbency Advantage

The regression discontinuity (RD) design is popular because it provides a design-based estimate of the incumbency advantage. However, the RD estimate is “local”: it only identifies the effect in hypothetical elections with a 50-50 tie between the Democratic and Republican candidates. There is significant uncertainty and disagreement over the incumbency effect in safer districts away from this threshold. Indeed, mirroring the competing arguments in the theoretical literature, a survey of political scientists reveals that roughly equal numbers of respondents predict the effect to be either larger, smaller, or the same in less competitive districts. We employ a new method based on a validated conditional independence assumption that allows us to estimate the effect of incumbency in districts in a window around the threshold as large as 15 percentage points—that is, elections in which the winning candidate secured as much as 57.5% of the two-party vote. We find that the incumbency advantage is no larger or sm...

The Changing Value of Seniority in the U.S. House: Conditional Party Government Revised

In this article, we argue that institutional changes to the seniority system have electoral consequences to incumbents. Building on the theory of Conditional Party Government, we argue that the consolidation of power in the hands of party leadership reduces the electoral value of seniority. This reduction occurs because power that was previously in the hands of committee chairs, whose roles are obtained through seniority, is ceded to party leaders. By increasing the party’s brand, this centralization also delivers a dividend received by all members regardless of seniority. We present empirical evidence supporting this argument. Our findings suggest that the “condition” of Conditional Party Government, i.e., preference homogeneity among the majority party, is only a necessary condition; in order for centralization to occur, party reformers must also overcome the opposition of entrenched senior members.

A novel Ruminococcus gnavus clade enriched in inflammatory bowel disease patients

BackgroundInflammatory bowel disease (IBD) is characterized by chronic inflammation of the gastrointestinal tract that is associated with changes in the gut microbiome. Here, we sought to identify strain-specific functional correlates with IBD outcomes.MethodsWe performed metagenomic sequencing of monthly stool samples from 20 IBD patients and 12 controls (266 total samples). These were taxonomically profiled with MetaPhlAn2 and functionally profiled using HUMAnN2. Differentially abundant species were identified using MaAsLin and strain-specific pangenome haplotypes were analyzed using PanPhlAn.ResultsWe found a significantly higher abundance in patients of facultative anaerobes that can tolerate the increased oxidative stress of the IBD gut. We also detected dramatic, yet transient, blooms of Ruminococcus gnavus in IBD patients, often co-occurring with increased disease activity. We identified two distinct clades of R. gnavus strains, one of which is enriched in IBD patients. To study functional differences between these two clades, we augmented the R. gnavus pangenome by sequencing nine isolates from IBD patients. We identified 199 IBD-specific, strain-specific genes involved in oxidative stress responses, adhesion, iron-acquisition, and mucus utilization, potentially conferring an adaptive advantage for this R. gnavus clade in the IBD gut.ConclusionsThis study adds further evidence to the hypothesis that increased oxidative stress may be a major factor shaping the dysbiosis of the microbiome observed in IBD and suggests that R. gnavus may be an important member of the altered gut community in IBD.

The Majority-Party Disadvantage: Revising Theories of Legislative Organization

Dominant theories of legislative organization in the U.S. rest on the notion that the majority party arranges legislative matters to enhance its electoral fortunes. Yet, we find little evidence for a short-term electoral advantage for the majority party in U.S. state legislatures. Furthermore, there appears to be a pronounced downstream majority-party disadvantage . To establish these findings, we propose a technique for aggregating the results of close elections to obtain as-if random variation in majority-party status. We argue that the results from this approach are consistent with a phenomenon of inter-temporal balancing, which we link to other forms of partisan balancing in U.S. elections. The article thus necessitates revisions to our theories of legislative organization, offers new arguments for balancing theories, and lays out an empirical technique for studying the effects of majority-party status in legislative contexts.

The Elusive Quest for Convergence

Does American political representation work as predicted by theory? On average, political candidates diverge considerably in their ideological positioning, but do they diverge less on issues of particular salience to their local constituents? We combine data on congressional roll call votes, electoral outcomes, district demographics, and substantive information about bills to search for convergence in the places we would most expect to find it. Despite the predictions of prominent models, legislators diverge just as much even when their constituents have strong interests in a particular policy area. These results provide new insights into policymaking and political representation, and they help distinguish between different theoretical explanations for why candidate positions diverge.