More Party Competition Predicts Higher Polarization — New Data Confirms Surprising Trend

How does party competition affect polarization? This article explores that question by analyzing state legislative data.

The Big Question: Does more political party competition lead to less polarization?

Researchers have long debated this relationship, but until now, no one had examined it systematically using comprehensive data on the 50 U.S. states.

New Insights from State-Level Data:

The study employs five distinct measures of partisan competition in state governments:

• Number of recent party control shifts
• Index measuring competition for state offices
• Presidential election closeness index
• Effective number of parties present
• Republican-to-Democrat voter ratio

Key Findings:

Contrary to older theoretical expectations (the so-called 'Competition-Cohesion' thesis), all five measures show a clear correlation: greater party competition is associated with higher levels of polarization in both state legislatures and general elections.

Why It Matters:

The findings challenge established assumptions about the relationship between electoral politics and legislative representation. They suggest that increased partisan competition at the state level does not moderate ideological differences among elected officials, but rather may intensify them.