Washington’s partisan wars may look like clashes between individual lawmakers, but new economic research argues the real power lies with the party bosses who script the fight—and the stalemate that follows. A study co-authored by University of Miami economist Chad Kendall concludes that most of the polarization tearing through Congress is generated by party organizations and their leaders, rather than by the personal ideological convictions of rank-and-file members.
The work builds on a series of papers in which Kendall and collaborators treat Congress like a vast data set, not a cable-news soap opera. In “Political Parties as Drivers of U.S. Polarization: 1927–2018,” co-authored with Nathan Canen and Francesco Trebbi, the team traces nearly a century of roll-call votes to separate what legislators want from what their parties demand. The research, developed through outlets such as the National Bureau of Economic Research and later published by the University of Chicago Press and in the Journal of Political Economy, positions parties—not just politicians—as key structural drivers of American polarization.
To pull that off statistically, Kendall and his colleagues compare how members vote on the House and Senate floor with the positions championed by party leadership, effectively measuring the gap between individual preference and party marching orders. One strand of their work uses detailed “whip count” data from 1977 to 1986—internal records tracking how parties pressure members before a vote—to quantify how often politicians diverge from their apparent ideology when the party turns the screws. In that period, the authors estimate that parties themselves account for roughly 40 percent of the polarization observed in legislative voting, a share large enough to alter which bills even make it onto the agenda.
More recent work by Kendall, including the “Party Pressure and Representation” working paper, goes further by explicitly modeling how party pressure distorts representation in the U.S. House. When that pressure is taken into account, standard measures of ideological polarization—such as the distance between the median Democrat and median Republican—change dramatically, suggesting that what looks like pure ideological sorting is often a product of party-enforced voting discipline. According to Kendall’s estimates, party pressure can explain a dominant share of measured polarization, reshaping both the likelihood that specific policies pass and the mix of bills party leaders choose to advance in the first place.
The University of Miami’s coverage of the study underscores how these dynamics translate into the daily grind of gridlock on Capitol Hill. As party organizations have become more skilled at disciplining defectors—through control of committee assignments, campaign resources, and leadership support—the willingness of members to cross party lines has steadily eroded since the late 1980s. That hardening of party discipline means that when party leaders decide to oppose each other, they can reliably marshal their caucuses behind maximalist positions, making bipartisan compromise and routine governance increasingly difficult. The result is a Congress where even broadly popular measures can stall because parties treat legislative bargaining as a zero-sum contest.
Kendall’s broader research program suggests the problem is not confined to the halls of Congress. In lectures and related papers, he explores how parties also drive polarization through rhetoric and narratives, showing that carefully crafted causal stories can foster false beliefs among voters and deepen both ideological and affective divides. Combined with evidence that voters themselves are increasingly sorted by party and ideology, these findings point to a feedback loop in which party organizations shape both what lawmakers do and how the public interprets those actions.
For anyone who thinks of politics like a strategy game, Kendall’s data-driven approach basically confirms what longtime players suspect: the “raid leaders” in Washington are the parties, not the individual characters on the screen. Party whips and leaders select the quests, set the win conditions, and penalize anyone who refuses to follow the chosen build. That might make for gripping spectator drama, but the research warns it also locks the system into stalemates where big problems go unresolved—not because no one cares, but because crossing party lines has become the ultimate forbidden move.
