Why do voters vote for third parties in single member districts? A test of four strategic voting conditions

Duverger’s law holds that single member district rules produce two-party systems, but third party voting remains an important feature of these institutional contexts. To explain the discrepancy between theory and empirical reality, Gary Cox specified four conditions are necessary for theoretical expectations to bear out. Yet, subsequent research has focused mostly on just one conditions, namely, voters have correct information about competitiveness their preferred in district. The purpose this paper is assess role all conditions. Using original survey data from 2015 United Kingdom general election, analysis suggests violations condition matter, short-term instrumental rationality can be a significant factor as well. Consequently, future should pay more attention when seeking voting.