This article analyzes why, despite similar transformations in the dimensions structuring political space since the late 1980s, extreme right-wing populist parties have emerged in some West European countries, but not in others. Two factors may affect the fortunes of these parties. First, if electorates remain firmly entrenched in older cleavages, new parties will find it difficult to establish themselves. Second, the positions of the established actors with respect to the new cultural divide that the extreme populist right mobilizes may be crucial. This article systematizes the various explanations regarding the impact of mainstream party positions on the electoral fortunes of the extreme right, and develops two new hypotheses that differentiate between the conditions that favor the entry of the extreme right, and its subsequent success. The various hypotheses are then tested in an empirical analysis of election campaigns in France and Germany, combining data on party positions as reflected in the news media with mass-level surveys. The results show that the diverging behavior of the established parties, rather than the strength of the traditional state-market cleavage, explains the differences between these two countries. More specifically, the differing strategy of the mainstream left in the two contexts has allowed the Front National to anchor itself in the French party system, whereas similar parties have not achieved a breakthrough in Germany.