While the sizeable literature on anti-immigrant parties commonly invokes the term “breakthrough” in discussing their electoral fortunes, no existing study has subjected this concept to conceptual or empirical scrutiny. Based on an investigation of 54 anti-immigrant parties in seventeen Western European countries, this paper concludes that these parties indeed tend to establish themselves with rare breakthrough elections rather than by incremental growth, and to stay around once they achieve such success. Moreover, these breakthroughs are more likely when these parties have direct or indirect ties to the party system. On the one hand, these findings confirm an often invoked but so far untested suspicion about the way these parties establish themselves. On the other hand, they have important implications for their future study. They suggest that some elections are more important than others for understanding the success of anti-immigrant parties, and that it is potentially misleading to explain the failure of anti-immigrant politicians in some places as the necessary consequence of country-specific characteristics. Not only can one unpredictable election change everything, the failure of anti-immigrant politicians in the past might also pave the way for like-minded politicians in the future.