Authoritarian regimes like China increasingly wield overseas propaganda as a tool of geopolitical competition. I introduce the concept of “political demonstration effects”: when information about a foreign country’s regime performance influences public attitudes toward democracy. I examine two messaging strategies―“autocratic advantage” messaging, which emphasizes the performance and procedural benefits of authoritarian governance, and “democratic disarray” messaging, which highlights the corresponding shortcomings of democratic systems. I evaluate the real-world prevalence of these strategies in China’s overseas propaganda, using an unsupervised machine learning approach to analyze 8.7 million tweets.1 I then test whether such propaganda shifts attitudes toward democracy through a multicountry survey experiment. I find that autocratic advantage messaging is both more prevalent and more effective at undermining public support for democracy. Despite a focus in academic and policy analysis on negative attacks, pro-regime propaganda matters, as it affects broader political attitudes, with implications for democratic backsliding and the playing field of US-China strategic competition.