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arXiv · 2607.14366

Stable Voting is PSPACE-Complete

Ethan Dickey·Alexandros Psomas·Athina Terzoglou
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Abstract

Stable Voting and Simple Stable Voting, introduced by Holliday and Pacuit, are Condorcet-consistent voting rules defined recursively: a candidate wins if they would win after removing some opponent they beat, taking the pair with the largest margin first. The computational complexity of winner determination under these rules has been an open question. We resolve this problem: winner determination is PSPACE-complete under both Stable Voting and Simple Stable Voting.

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Ethan Dickey, Alexandros Psomas, Athina Terzoglou. 2026-07-15. Stable Voting is PSPACE-Complete. https://arxiv.org/abs/2607.14366

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