Candidate-centered electoral systems are often assumed to encourage personal vote-seeking, but how we measure intra-party competition matters. This article uses 1,394 campaign brochures from South Korea’s 2022 local council elections under SNTV to test whether co-partisan rivalry drives particularistic appeals. I find that the co-partisans-to-magnitude ratio (C:M) increases particularistic promises, while the co-partisans-to-expected-seats ratio (C:E) does not. Interviews show that parties often nominate candidates based on short-term sentiment rather than past seat shares, explaining C:E’s limits. The study highlights how measurement choices reshape our understanding of candidate strategies in comparative politics. 

This study examines how single non-transferable voting (SNTV), one of the most candidate-centered electoral systems, shapes legislative corruption. Using data on South Korean local councils (2013–2023) and a causal forest approach, I show that higher intra-party competition within districts is associated with significantly greater corruption. These findings underscore the importance of electoral system design and reveal how intra-party rivalry can exacerbate governance failures.