A prominent explanation of war claims that international conflict can result when shifts in bargaining power induce the declining power to behave aggressively today because the rising power cannot credibly commit to not behave aggressively tomorrow. This paper asks whether individuals respond to shifting power in ways assumed by these models. Rather than use abstract laboratory-based bargaining games as in other work, I use vignettes describing the United States in an international bargaining situation to explore the microfoundations of power transitions models empirically. The vignettes vary whether the individual is a member of a declining or a rising power and whether there are previous public commitments to the status quo division of territory. Subjects propose a response the United States should make and then explain their decision in their own words. I apply new methods for analyzing these openended responses. Consistent with predictions from the behavioral literature, I find important asymmetries in behavior across these conditions as well as substantial heterogeneities in individuals' motivations for their decisions. The results of the experiments suggest potential ways that power-transition models should be refined to have a firmer behavioral basis.A prominent explanation for why conflict occurs between countries is shifting power: states that are declining in power may act belligerently to prevent a decline and states that are increasing in power cannot credibly commit to not taking advantage of their new-found power in the future. A large literature has developed that describes why and how the dynamics of shifting power explain international conflict, ranging from power transition theory to formal accounts emphasizing commitment problems. 1 This literature largely adopts a "billiard ball" view of the state in which the influence of the public and domestic politics, as well as elite perceptions of both the internal and external environment, is bracketed. This approach contrasts with other literatures that have described mechanisms through which the public and domestic politics affect both international outcomes 2 and intrastate conflict. 3 This paper combines the theoretical and empirical motivations of both sets of literatures. It is the first to directly examine whether the public holds views that are My thanks to Nehmia Geva, Iain Johnston, Rose McDermott, Brian Rathburn, Jonathan Renshon, Molly Roberts, Robert Schub, Brandon Stewart, and Michael Tomz for illuminating conversations, participants in the TAMU IR workshop, and participants at the 2014 UCSD Behavioral International Relations conferences. I am especially grateful to Steph Haggard for multiple rounds of detailed comments.