Strategic voting in established and new democracies: Ticket splitting in mixed-member electoral systems

Using Cox's ’SF-ratio’ (the ratio of the vote won by the ’second loser’ to that of the ’first loser’), we examine strategic voting in mixed-member electoral systems in ten countries and a total of 35 elections. The SF-ratio is a useful indicator of strategic defection from less competitive to more competitive electoral options that is comparable across very diverse country cases. Under conditions of a Duvergerian equilibrium, where there is substantial information indicating which candidate is likely to end up the top challenger to the frontrunner, the SF-ratio for a district will tend toward zero. In contrast, in cases where voters either are unwilling or unable to cast strategic ballots, SF-ratios will tend to be higher. Our findings show substantial evidence of strategic voting in established democracies, particularly in districts with closer races, but little evidence of strategic voting in new democracies with poorly institutionalized party systems.