This study investigates the reciprocal relationships between tolerance and democracy. It examines how tolerance influences democracy and how democratic socialization influences tolerance. The concept of tolerance often becomes most important when it is weakened or missing. Intolerance presents a problem not only to less democratic countries but to established democracies as well. Its effects are visible in many ways, including support for illiberal political parties that, where sufficiently influential, can establish rejectionist and exclusionary policies. While threats to tolerance as a hallmark of liberal democracy appear in different forms across a wide range of countries, the present study analyzes contemporary European cases. There in/tolerance has an especially important place in political communication, with xenophobia fueling the success of influential parties in old and new democracies alike. Based on contemporary theoretical and empirical debates, this study’s first goal is to analyze causal connections between (in)tolerance, satisfaction with democracy, party system characteristics, type of electoral system, partisan preferences, and democracy. A second and necessary purpose of this study is to identify the importance of a previously unexplored potential contributor to tolerance: temporary migration. This dissertation offers an original test of the impact of temporary migration on tolerance. It confirms through empirical evidence that migration to more democratic countries than one’s country of origin enhances tolerance via the process of democratic socialization. The findings of this dissertation are based on a blend of primary and secondary sources and uses a multi-method empirical approach in order to investigate the research questions posed.