Open Access

Martin Rachuj

• The study at hand examines the phenomenon of new parties. It aims to answer the research question of whether established parties can influence the electoral success of new competitors with their election programs. With the entrance of a new party, a new competitive structure must be considered by the established parties. The theory developed here suggests that these parties may respond to this challenge by changing positions and selectively emphasizing issues, thereby changing the assessment of voter proximity, the attribution of issue ownership, and the public agenda, which ultimately contributes to changing the vote shares of new parties. The study analyses 168 new parties in 18 advanced democracies using electoral data (Jahn et al., 2018a) and party manifestos (Krause et al., 2018; Volkens et al., 2020). A text‐analytic approach is adopted, which is validated by an innovative simulation experiment that generates synthetic manifestos. Based on the calculation of the textual similarity of election manifestos and multilevel regression analysis, the study shows which strategies of established parties are effective in the face of new challengers and which are not. The results show that established parties are not out of options but can influence the vote share of the new contenders by changing their selective issue emphasis. The effect of a shift in the issue profile of an established party depends strongly on the concurrent competitive situation: Both ideological proximity and the expected election outcome play an essential role. Established parties successfully fight new parties with an engagement strategy if they act from a position of strength, i.e., if their vote gains are in prospect. Furthermore, the ideological proximity of the new party should be taken into account when choosing the strategy: within the same ideological bloc, an engagement strategy can be pretty successful; outside the bloc, this is instead not the case. Furthermore, policy moves of established parties measured on the left‐ right dimension do not affect the vote share of new parties. The text‐as‐data approaches in general, and the text‐similarity analysis, in particular, contribute to a better understanding of the dynamics of party competition between established forces and their new competitors. Furthermore, the chosen methodological approach and theoretical basis are not limited to this field but can be applied more generally to the analysis of the dynamics of party competition between all parties in a party system. In conclusion, this thesis contributes to a better understanding of the field of party research, quantitative text analysis, and computational social science.