There is now substantial evidence that defense spending decisions in the United States are influenced by citizen preferences. However, there is little time-series evidence for countries other than the United States. Regression models of citizen responsiveness and opinion representation in the politics of defense spending in five democracies are estimated. Results show that public opinion in all five countries is systematically responsive to recent changes in defense spending, and the form of the responses across countries uniformly resembles the “thermostat” metaphor developed by Wlezien and the more general theory of opinion dynamics developed by Stimson. Findings show also that defense budgeting is representative: public support for defense spending is the most consistently significant influence on defense budgeting change in four countries; thus, a parsimonious theory of comparative policy representation is potentially within reach. The implications of the results for defense spending in the NATO alliance and the European Union are discussed.