Modern democracies face increasing challenges from psychological manipulation, misinformation, emotional polarization, and identity-based mobilization. While traditional defenses of democratic systems focus on legal institutions, military security, and electoral processes, an emerging body of research suggests that psychological resilience within society is equally critical for democratic stability. This paper introduces the concept of Psychological Defense of Democracy (PDD)—a multidisciplinary framework that integrates behavioral science, cognitive psychology, communication research, and governance strategies to protect democratic institutions and civil liberties from manipulation. The study identifies key psychological triggers that influence public perception and social mobilization, proposes behavioral markers that can help authorities detect emerging threats to democratic stability, and outlines corrective strategies for strengthening societal resilience when warning indicators appear. The paper also explores how psychologists, researchers, educators, and policy-makers can collaborate to build early detection and intervention systems that protect democratic societies without undermining individual freedoms.