2025 Theses Doctoral

Essays in Political Economy

Longuet-Marx, Nicolas

This dissertation is a collection of five essays that examine the forces shaping contemporary U.S. political competition, with a focus on voter realignment, party strategy, policy diffusion, and democratic attitudes. It traces how shifts in voter preferences, party positioning, and institutional dynamics have reconfigured electoral coalitions, shaped legislative developments, and influenced political responses to major shocks, such as climate change and the Covid-19 crisis. The analysis draws on theory, newly assembled historical and contemporary datasets, survey experiments, and both reduced-form and structural estimation to uncover key mechanisms in political economy.

The first chapter estimates a political equilibrium model to disentangle demand factors (voters) from supply factors (politicians) in shaping political outcomes, focusing on the recent realignment of blue-collar voters away from left-wing parties. I jointly evaluate the impact of changes in voter preferences and voter demographics (demand side) and party positions and party discipline (supply side) on voters’ partisan realignment in U.S. House elections between 2000 and 2020. To measure candidate ideological positioning, I estimate a multimodal text-and-survey model from campaign websites. To estimate voter preferences, I build a new panel of precinct-level election results (N=1.3 million), which allows me to exploit congressional districts' border discontinuities for identification. The paper ultimately identifies parties’ stronger polarization on cultural issues compared to economic issues as the main driver of voters’ partisan realignment. In contrast, shifts in voter preferences—particularly the increasing preferences of blue-collar voters for progressive economic policies—have mitigated their defection from the Democratic Party. Absent these demand-side changes, voters’ partisan realignment would have been even more pronounced. Within specific policy domains, the environment emerges as the topic where parties diverge most in economic versus cultural emphasis: Democrats frame it culturally, while Republicans focus on economic aspects. Simulations reveal that a progressive, economically focused environmental policy would gain greater blue-collar voter support than a culturally focused one.

The second chapter examines the same question from a historical perspective, tracing partisan realignment by education back to World War II. It argues that the Democratic Party’s evolution on economic policy helps explain partisan realignment by education. We show that less-educated Americans differentially demand ``predistribution’’ policies (e.g., a federal jobs guarantee, higher minimum wages, protectionism, and stronger unions), while more-educated Americans differentially favor redistribution (taxes and transfers). This educational gradient in policy preferences has been largely unchanged since the 1940s. We then show the Democrats’ supply of predistribution has declined since the 1970s. We tie this decline to the rise of a self-described ``New Democrat’' party faction who court more educated voters and are explicitly skeptical of predistribution. Consistent with this faction’s growing influence, we document the significant growth of donations from highly educated donors, especially from out-of-district, who play an increasingly important role in Democratic (especially ``New Democrat'') primary campaigns relative to Republican primaries. In response to these within-party changes in power, less-educated Americans began to leave the Democratic Party in the 1970s, after decades of serving as the party’s base. Roughly half of the total shift can be explained by their changing views of the parties’ economic policies. We also show that in the crucial transition period of the 1970s and 1980s, New Democrat-aligned candidates draw disproportionately from more-educated voters in both survey questions and actual Congressional elections.

The third chapter estimates an empirical model of adoption and diffusion of policies across U.S. states since 1787. We use a large language model to extract and structure the policy content of the universe of statutes enacted by state legislatures (N=2.5 million). We then construct sets of related policies across states using an unsupervised clustering algorithm applied to vector representations of the statutes' policy contents. We compute measures of similarity, diffusion, and innovation across states with legislative activity on these policy clusters. After validating this measurement procedure, we analyze the determinants of diffusion. We find that states with greater geographic, economic, and political similarity implement more similar policies. While polarization has risen significantly since the 1990s, consistent with prior literature, we show that current levels of polarization are comparable to those observed in the pre-WWII period, following a U-shaped pattern over time. Polarization primarily reflects differences in policy choices within topics rather than in the topics on which states choose to legislate. Finally, we document an increasing nationalization of policy, with federal legislative texts exerting growing influence on state legislation since the post-war period.

The fourth chapter studies the effects of climate change and mitigation on U.S. politics. We combine 2000-2020 precinct-level voting information and congressional candidate positions on environmental policy with high-resolution temperature and precipitation data and census block-group level measures of ``green" and ``brown" employment shares. Holding politician positions fixed within a district, we find that Democratic vote share increases with exogenous changes in local climate and green transition employment. We embed these estimates into a structural model of political competition, including both direct and demand-driven effects of shocks on candidate policy platform supply. Incorporating our model estimates into 2025-2050 projections of climate change and green employment transition, we find that voting for the Democrats increases, while both parties move slightly to the right on climate policy. Under worst-case climate projections and current mitigation trajectories, the median 2050 Congressperson has roughly the same environmental ideology as the median 2010 Democrat---for instance supporting carbon pricing.

The fifth chapter studies how crisis of the magnitude of the Covid-19 pandemic may plausibly affect deep-seated attitudes of a large fraction of citizens. In particular, outcome-oriented theories imply that leaders' performance in response to such adverse events shapes people’s views about the government and about democracy. To assess these causal linkages empirically, we use a pre-registered survey experiment covering 12 countries and 22,500 respondents during the pandemic. Our design enables us to leverage exogenous variation in evaluations of policies and leaders with an instrumental variables strategy. We find that people use information on both health and economic performance when evaluating the government. In turn, dissatisfaction with the government decreases satisfaction with how democracy works, but it does not increase support for non-democratic alternatives. The results suggests that comparatively bad government performance mainly spurs internal critiques of democracy.