Publicize or Perish—Challenger party success through megaphones and locomotives.

What makes some challenger parties succeed and others fail? Existing research on party‐level factors finds that it is essential for parties to close a representational gap. However, this condition cannot be sufficient. For each successful challenger, there are many others proclaiming a similar message but going unheard. Hence, we argue that, instead of only to the messages, more attention should be paid to parties' abilities to communicate their messages effectively. Using an original dataset on 74 challenger parties in five countries in a similar political and economic situation (during the post‐2008 economic crisis), we show that communication is key for electoral success. In particular, we show that challenger parties can win over voters by, on the one hand, harnessing the prominence of a well‐known personality (a locomotive) and by, on the other hand, establishing a means of contacting voters which bypasses the traditional news media and amplifies their message (like a megaphone). But this megaphone only works if it amplifies a message that fills a representational gap (here: an anti‐austerity message) – only then do parties benefit. Furthermore, we provide evidence for the widespread but unproven claim that populism helps challenger parties succeed, but this, too, depends on whether parties are able to contact voters on a large scale. By including three crucial aspects of communication (sender, channel, and message), we can explain a large share of the high variability in challenger party success. [ABSTRACT FROM AUTHOR]