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Does Ideological Polarization Lead to Policy Polarization?

Philipp Denter

TL;DR

The paper investigates how ideological polarization shapes policy polarization in a two-party electoral competition where parties are fixed on ideology but free to choose a continuous policy position. It develops a Bayesian Nash equilibrium framework with uncertainty in ideology and valence, showing that policy polarization evolves non-monotonically with ideological polarization $w$, forming a U-shaped relationship with moderation at low $w$ and amplification at high $w$. It further clarifies valence effects, showing that high-valence advantages may lead to more extreme policies in low-polarization contexts but can reverse in highly polarized environments. These results provide a theoretical explanation for empirical patterns where ideological and policy polarizations diverge and have implications for the dynamics of political competition in polarized democracies.

Abstract

I study an election between two ideologically polarized parties that are both office- and policy-motivated. The parties compete by proposing policies on a single issue. The analysis uncovers a non-monotonic relationship between ideological and policy polarization. When ideological polarization is low, an increase leads to policy moderation; when it is high, the opposite occurs, and policies become more extreme. Moreover, incorporating ideological polarization refines our understanding of the role of valence: both high- and low-valence candidates may adopt more extreme positions, depending on the electorate's degree of ideological polarization.

Does Ideological Polarization Lead to Policy Polarization?

TL;DR

The paper investigates how ideological polarization shapes policy polarization in a two-party electoral competition where parties are fixed on ideology but free to choose a continuous policy position. It develops a Bayesian Nash equilibrium framework with uncertainty in ideology and valence, showing that policy polarization evolves non-monotonically with ideological polarization , forming a U-shaped relationship with moderation at low and amplification at high . It further clarifies valence effects, showing that high-valence advantages may lead to more extreme policies in low-polarization contexts but can reverse in highly polarized environments. These results provide a theoretical explanation for empirical patterns where ideological and policy polarizations diverge and have implications for the dynamics of political competition in polarized democracies.

Abstract

I study an election between two ideologically polarized parties that are both office- and policy-motivated. The parties compete by proposing policies on a single issue. The analysis uncovers a non-monotonic relationship between ideological and policy polarization. When ideological polarization is low, an increase leads to policy moderation; when it is high, the opposite occurs, and policies become more extreme. Moreover, incorporating ideological polarization refines our understanding of the role of valence: both high- and low-valence candidates may adopt more extreme positions, depending on the electorate's degree of ideological polarization.

Paper Structure

This paper contains 15 sections, 5 theorems, 51 equations, 6 figures.

Table of Contents

  1. Introduction
  2. Literature:
  3. Model
  4. Discussion of Assumptions:
  5. Ideological and Policy Polarization
  6. Valence Advantages and the Moderate Frontrunner
  7. Conclusion
  8. Mathematical Appendix
  9. Proof of Proposition \ref{['prop:1']}
  10. $\sigma_i\rightarrow 0$:
  11. $\sigma_v\rightarrow 0$:
  12. Proof of Proposition \ref{['prop:sym_EQ']}
  13. Proof of Proposition \ref{['prop:dDeltedw']}
  14. Proof of Proposition \ref{['prop:asym']}
  15. Proof of Proposition \ref{['prop:asym2']}

Key Result

Proposition 1

Consider the two polar cases in which there is only one source of uncertainty. Let $\Delta(w) = \left|p_R^*(w) - p_L^*(w)\right|$ denote policy polarization. Then:

Figures (6)

  • Figure 2: Platform polarization $\Delta(w)$ in the symmetric equilibrium as a function of $w \in [0,2]$ for varying $\sigma_i$.
  • Figure 3: Combinations of $\mu_v$ and $\mu_i$ such that a symmetric equilibrium exists for $w \in \{\tfrac{1}{2}, 1, 2\}$.
  • Figure 4: Platform choices as a function of $w$ when party 1 has a valence advantage and party 2 an ideological advantage (left panel). Platform polarization $\Delta(w)$ in the asymmetric equilibrium as a function of $w \in [0,3]$ (right panel).
  • Figure : (a) Affective polarization of voters.
  • Figure : (a) Affective polarization of voters.
  • ...and 1 more figures

Theorems & Definitions (5)

  • Proposition 1
  • Proposition 2
  • Proposition 3
  • Proposition 4
  • Proposition 5