A Sum of Its Parts: Party Fit and Party Change in the U.S. House

• Published date: 01 September 2021
• DOI: 10.1177/1532673X211006824
• Date: 01 September 2021
• Subject Matter: Articles

https://doi.org/10.1177/1532673X211006824

American Politics Research

2021, Vol. 49(5) 464 –477

© The Author(s) 2021

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DOI: 10.1177/1532673X211006824

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Article

Introduction

One of the most prominent patterns in contemporary

American politics is the transformation of the major parties

in the U.S. Congress since the 1970s, as exhibited in their

increased ideological polarization (McCarty et al., 2008),

transformation on social issues like civil rights, abortion, and

the environment (Adams, 1997; Carmines & Stimson, 1989;

Shipan & Lowry, 2001), and increased polarization on a

wider range of issues (Layman & Carsey, 2002). Several

works have assessed what factors have contributed to the

transformation of the parties, including the impact of social

groups, party activists, gerrymandering, campaign money,

and the exercise of institutional powers by party leadership

(e.g., Cox & McCubbins, 2005; Karol, 2009; McCarty et al.,

2008; Theriault, 2006). Closely related to our paper, Thomsen

(2017) analyzes how the strategic career choices of party

members have contributed to an increasingly polarized U.S.

House. She finds that ideological fit with the party impacts

career decisions, as increasingly polarized parties in the

House contributes to the disappearance of moderates—that

is, fewer moderate candidates and more moderates retiring

from Congress.

Our paper uses a different approach to assess the central

tendency of the party and analyzes the impact of party fit on

retirement decisions that contribute to and reinforce party

change in the U.S. House.1 In short, as the centrality of the

party shifts over time, members decide whether to remain in

office or retire depending on whether they are toward the

core of the party. Those career decisions therefore reinforce

and contribute to changes in the parties. Our paper makes

several significant contributions. We analyze bill cosponsor-

ship behavior in the U.S. House from the 93rd to 110th

Congresses and view the party as a social network in which

members are connected if they both cosponsor the same bill,

which has both theoretical and empirical benefits that we dis-

cuss below. Only briefly stating two benefits here, analyzing

cosponsorship (a) provides a more thorough picture of inter-

actions among party members, which we take as “defining

the party” and indicating who are most central in the party,

and (b) constructs an empirical measure of party fit that

accounts for the individual choices of members and how the

party is an aggregation of those choices.

Our paper has two main goals. First, we descriptively

show how the cosponsorship networks of the parties in the

U.S. House have changed since the 1970s. Our analysis

shows that cosponsorship behavior can indeed provide a use-

ful metric to describe the party, as it is related to but distinct

from roll call voting behavior and (revealed) ideology.

Second, we analyze the impact network centrality has on

member retirement from office, showing that low centrality

1006824APRXXX10.1177/1532673X211006824American Politics ResearchLee and Go

research-article2021

1University of Nevada, Las Vegas, USA

Corresponding Author:

Daniel J. Lee, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy,

Box 455029, Las Vegas, NV 89154-9900, USA.

Email: dan.lee@unlv.edu

A Sum of Its Parts: Party Fit and Party

Change in the U.S. House

Daniel J. Lee1 and Sean M. Goff1

Abstract

Previous research has noted the transformation of the American parties since the 1970s, as exhibited in their increased

ideological polarization and transformation on social issues like civil rights, abortion, and the environment. We contribute

to the literature on party change by theoretically stressing the decentralized and individualistic nature of American parties,

while using a measure of party change that is based on legislative behavior beyond roll call voting. Our paper uses social

network analysis to analyze the parties from the 93rd to 110th Congresses, utilizing bill cosponsorship to define connections

between members. Our analysis illustrates how the core of the party, that is, who are most central in the cosponsorship

network, has changed over time. We find evidence that party centrality influenced retirement decisions, thereby reinforcing

and contributing to party change.

Keywords

political parties, party change, legislative behavior, cosponsorship