This study compares the relative importance of two perspectives on issue evolution: is the emergence of new issues partly explained by societal factors such a trends, events and public opinion, or is this process entirely driven by the strategic incentives of politicians? By means of time-series analysis between 1974 and 2003, this “crucial case study” on the politicization of the immigration issue in Denmark demonstrates that societal imputs can hardly explain why new issues reach the political agenda. On the other hand, the results provide convincing evidence that issue competition dynamics between anti-immigrant parties, mainstream opposition parties and mainstream government parties have driven the politicization of the immigration issue in Denmark. In contrary, to popular explanations for niche party success that have focused on the incentives of the mainstream right, this study shows that anti-immigrant parties set in motion the sequence of politicization. Consequently, current explanations on the politicization of niche party issues remain incomplete if the agency of the niche party itself is not considered. The results have important implications for the literature on issue evolution, dynamic representation and niche parties.
