When Does Audience Matter? Challengers' Stability and Audience Costs

In this article, we argue that the degree to which audience costs work depends on the challenger state's leader stability. Unlike in the previous literature, we attempt to depart from a simple categorical comparison among regime types. Instead, we argue that the magnitude of audience costs varies continuously throughout the spectrum of a leader's stability. We employ probit regression with a squared term of stability, utilizing a large-N dataset of international conflicts provided by Militarized Interstate Dispute. Empirical results suggest a U-shaped curvilinear relationship between a challenger's stability and a target's probability of reciprocation. As the challenger's stability decreases, a target of interstate military conflict is less likely to reciprocate, that is, audience costs are more likely to be generated when a challenger is less stable. However, a target is less likely to concede as stability goes below a certain level because outside actors cannot learn the challenger's political patterns and intentions. Such findings imply that audience costs would be the highest at a moderate level of instability.