Do two parties represent the US? Clustering analysis of US public ideology survey

TL;DR

This study uses clustering analysis on US public opinion data to evaluate how well two major parties represent the public's ideology and explores whether a multiparty system offers a better representation.

Contribution

It applies Gaussian Mixture Model clustering to survey data to compare two-party and multiparty representations of public ideology.

Findings

Two main ideological clusters: centrist and right-wing.

Major parties' positions align with these clusters.

More than two clusters better fit the data, indicating multiparty systems may better represent public opinion.

Abstract

Recent surveys have shown that an increasing portion of the US public believes the two major US parties adequately represent the US public opinion and think additional parties are needed. However, there are high barriers for third parties in political elections. In this paper, we aim to address two questions: "How well do the two major US parties represent the public's ideology?" and "Does a more-than-two-party system better represent the ideology of the public?". To address these questions, we utilize the American National Election Studies Time series dataset. We perform unsupervised clustering with Gaussian Mixture Model method on this dataset. When clustered into two clusters, we find a large centrist cluster and a small right-wing cluster. The Democratic Party's position (estimated using the mean position of the individuals self-identified with the parties) is similar to that of the centrist cluster, and the Republican Party's position is between the two clusters. We investigate if more than two parties represent the population better by comparing the Akaike Information Criteria for clustering results of the various number of clusters. We find that additional clusters give a better representation of the data, even after penalizing for the additional parameters. This suggests a multiparty system represents of the ideology of the public better.