The theory of issue evolution or issue manipulation holds that parties that lose put new or old issues (back) on the political agenda to upset the existing system of party competition. This is an important mechanism for representation, because after losing parties can bring the party platform closer in line with the public’s political preferences. However, empirical studies – mostly looking at electoral defeat – reach mixed conclusions regards its impact on party platform change. We reach back to the original meaning of losing, conceptualized as losing bargaining power over the agenda and propose three mechanisms by which this takes place: losing elections, losing office and party leadership change. We subsequently propose a new way of measuring party platform change that alleviates the problems of studies that look at a general left-right scale or a specific issue. We test our hypotheses using 1488 party platform changes in the period 1950-2010 in 18 advanced democracies. We find evidence that losing elections and leadership change are important predictors for party platform change, but these effects are also moderated by electoral systems, party organization and they differ over time.
