Preface -- Diversity dilemmas in democratic representation -- Internal valuation within political organizations: political parties and gender-based group dynamics in the U.S. House of Representatives -- A unified theory of colleague valuation in political organizations -- Testing the unified theory of colleague valuation in the U.S. House of Representatives -- Coordination dilemmas and the critical mass problem: differentiating colleague valuation between incumbents and challengers in the U.S. Senate -- Can organizational mechanisms solve minority group coordination problems? logic, lessons, and evidence from legislative caucuses in the American states -- The organizational foundations of democratic representation.