Building on scholarship that seeks to explain sincere voting in electoral context, this paper investigates whether system openness, defined by the complex of electoral institutions which shape party system dynamics like district magnitude, proportional seat allocation and legal thresholds, has consequences for voters’ decisions to remain loyal to their preferences. I begin by asking under what circumstances we should expect voters to be loyal to their preferences, identifying three baseline correlates of sincerity. I then investigate the extent to which such conditions hold when placed in the proper electoral context. The study makes use of matched vote choice and party preference data from respondents across 18 advanced democracies compiled by the Comparative Study of Electoral Systems (CSES). I find that small party supporters are more likely to cast sincere ballots when they have strongly positive feelings for their party and when their affect toward the top two parties differs little. By contrast, when voters are less positive about their party and especially when they perceive a large difference between the top alternatives, they are much more likely to stray. Finally, institutional characteristics alter these relationships, with more open electoral systems strengthening the relationship between affect and sincerity, and weakening the pressure to cast strategic ballots when the top alternatives seem very different. These results provide generalized support for previous work linking sincerity levels to permissive electoral arrangements, while providing a contextualized understanding of how electoral institutions can impact voter rationale.

An ongoing debate in political science research focuses on the degree to which democratic party systems are stable. One camp of authors argues that political cleavages in party systems endure, and thus party systems themselves show few significant signs of increased instability. Another group of authors argues that since the 1970s, political cleavages have weakened, and accordingly, system stability has decreased. My research continues this debate. I suggest that part of the uncertainty surrounding the direction and magnitude of stability trends results from the contrasting methodologies researchers have employed. I solve this difficulty by replicating the data and methods that Rose and Urwin employed in their 1970 study. By using identical measures of electoral change, I can ensure that any trends I find are not due to measurement artifacts. I compare their results from the period 1945-1970 with a new set of results for the 1970-1995 period for the same countries, extending the analysis far beyond other recent studies of partisan stability.