In this paper, we advance the argument that the support of electoral constituencies moderates political elites’ propensity to uphold the defence mechanisms of military alliances. We present evidence from a survey experiment administered to members of national parliaments (MPs) in seven NATO countries. In the experiment, we envision a scenario whereby pro-Russian military forces attack a NATO member (Estonia) manipulating whether voters of the MP’s own political party support or oppose a potential military intervention to assist Estonia in restoring security. Our study provides three key contributions. First, by experimentally investigating elite positions on the use of force and alliances, we contribute to a relatively scarce body of literature, highlighting whether public opinion influences political elites’ support for military engagement and other policy responses. Second, we offer novel theoretical insights about the policy preference “disconnects” between voters and politicians, showing how electoral incentives can moderate ideological positions on relevant international issues. Finally, our analysis sheds light on the relationship between military alliances, public opinion and foreign policy decision-making amidst renewed international tensions in Europe and the prospect of potential US disengagement.