We explore theoretically and empirically the implications of the political party's candidate selection systems on politicians’ incentives. Through a contract theory model for the problem of multiple principles and an agent with multi-task, we have shown that the bottom-up nomination system is socially optimal, and the politician's effort for re-election under the top-down nomination system is much less than social optimal. By utilizing the partial introduction of the bottom-up nomination system in the 17th general election, we empirically have found that the legislative effort of politicians elected through bottom-up nomination is greater than that of politicians elected through top-down nomination.

Preface
Executive Summary

Chapter 1 Introduction
Chapter 2 Candidate Selection Systems and Political Accountability: Theory
　Section 1 Literature Review
　Section 2 Model
　Section 3 Socially Optimal Solution
　Section 4 Nomination and Re-Election Mechanisms
　Section 5 Conclusion and Policy Implications

Chapter 3 Nomination Systems and Legislative Effort: Evidence
　Section 1 Background
　Section 2 Literature Review
　Section 3 Methods and Data
　Section 4 Nomination Systems and Characteristics of Legislators
　Section 5 Nomination Systems and Legislative Effort
　Section 6 Conclusion

Chapter 4 Conclusion

References
ABSTRACT