Democracies are under pressure worldwide: The political landscape is rapidly changing, with new parties emerging and old ones suffering, as voters turn away from established parties. We also witness a significant gender-gap in political endurance, meaning that women’s careers as elected representatives in parliaments tend to end quicker than men’s. SUCCESS argues that questions of women’s political endurance are of uttermost importance for the quality and legitimacy of democratic processes and therefore demand scholarly attention. SUCCESS will advance a novel theory of inclusion that explains gender-gaps in endurance, and provide much-needed new empirical evidence on why, how and under what conditions women’s political careers are likely to endure. SUCCESS will investigate the multifaceted relationships between a) the agency of elected representatives, i.e. their choice of strategies to get re-elected b) popular opinions about representatives’ gender, political experience and their career strategy, and c) the specific institutions and contexts that underpin gender-gaps in political endurance across time, regions and political systems. SUCCESS thus offers a comprehensive perspective, highlighting the interconnections between these three aspects in a novel theory of political inclusion: Rather than focusing on what excludes women from political office, the project explores what contributes to their success. SUCCESS will employ a unique multi-methods approach to collect data in five core country cases and a large-N dataset, including qualitative interviews, survey experiments, conjoint analysis, simulation study and anthropological film. These efforts yield unprecedented opportunities for a new turn towards understanding how gender-gaps in political endurance affect political inequalities. The project is pioneering empirical studies on why and how increased electoral volatility in new and old democracies disrupts or reinforces gendered power hierarchies in politics.