Who Supports Sanseito, and How Stable Is That Support?

Online appendix for: Matsubayashi, Tetsuya, Hazumu Ono, Masahiro Zenkyo, and Kohei Nishi. 2026. “Who Supports Sanseito, and How Stable Is That Support?” Japanese Journal of Electoral Studies 42(2).This document provides supplementary information for the article, which examines the political characteristics of Sanseito supporters and the stability of their support using three-wave online panel survey data collected between July and November 2025.The appendix contains:Appendix 1: Details of the analysis of party positions on the economic and GAL-TAN dimensions (Figure 1), based on the UTokyo–Asahi Survey of 2025 House of Councillors election candidatesAppendix 2: Question wording and response options for the variables used in the analysisAppendix 3: Socioeconomic characteristics and Sanseito supportAppendix 4: Internal political efficacyAppendix 5: Changes in ideology and policy preferences between the July and November surveysAppendix 6: Evaluation of group differences using Cohen’s dAppendix 7: Numerical results underlying the figures in the main text (Figures 2–7)Appendix 8: Software used for the analysisThe document is written in Japanese.松林哲也・小野弾・善教将大・西耕平（2026）「参政党支持の分析：誰が支持し、どのくらい安定的か」『選挙研究』42巻2号の補遺。本補遺には、各政党のイデオロギー的立場に関する分析の詳細、分析に用いた質問文と回答選択肢、社会経済的属性と参政党支持の関係、内的有効性感覚の分析、7月調査時と11月調査時のイデオロギー・政策選好の比較、Cohen’s dによる評価基準、本文中の図に対応する数値表、および分析に用いたソフトウェアを収録している。