"Nationalist Protests, Government Responses, and the Risk of Escalation in Interstate Disputes" ABSTRACT: When does nationalist public sentiment increase the risk of war in interstate disputes? The literature often cites nationalism as a key driver of conflict, emphasizing elite willingness to pander to it and the resulting constraints on state action. But much less attention has been paid to variation in elite fears of popular nationalism and efforts to subdue rather than inflame such sentiments. We focus on one key form of nationalist expression—street protests—and the conditions under which nationalist mobilization may raise the risks of war amid interstate feuds, whether by harming foreign interests directly or forcing governments to adopt a more belligerent stance. When nationalist protesters demand confrontational or uncompromising policies, elites must weigh the costs and benefits of repression against those of allowing protests, including the risk that protests will lead to domestic instability or interstate conflict. We argue that governments’ ability and willingness to subdue hardline nationalist protests varies within and across regime types. In democracies, where the risks of allowing protests are relatively low and costs of repression are relatively high, demonstrations are common but rarely destabilizing: revealing citizen preferences but ultimately influencing foreign policy through the filter of elections. Autocracies typically forbid public protests that may unite opposition to the regime, since the cost of repression is usually lower than the risk to stability. Yet incentives to harness public opinion to advance territorial objectives and increase domestic legitimacy create windows of selective tolerance in authoritarian states, which can heighten interstate tension. Hybrid regimes may have enough democratic features to make repression costly but not enough to ensure the stable and peaceful resolution of domestic grievances, making nationalist protests both more common and more likely to force international escalation. To illustrate, we examine how four different regimes, ranging from autocratic to democratic—Vietnam, Cambodia, Thailand, and the Philippines—have dealt with nationalist protests over interstate disputes in recent years.