Open Seat refers to an elective office during an election cycle in which no incumbent office holder seeks re-election. Given the incumbency advantage in legislative elections in the United States and Japan, such races typically offer non-incumbents their greatest probability of winning office. As a consequence, the electoral competition for open seats is often more intense than in other races.
- David R. Mayhew. Congress: The Electoral Connection. (New Haven, Yale University Press, 1974).
- John Hickman. "The Effect of Open Seats on Challenger Strength in Japanese Lower House Elections" Legislative Studies Quarterly 17,4 (Nov. 1992), Pp. 573-584.