Why are some small parties successful whereas others wither away? Despite
the voluminous literature on parties and party families, we have a limited
understanding of what explains small party success. Most studies tend to
emphasize the role of social cleavages and electoral systems. Instead, we
propose a new institutional explanation that treats entering parliament as a
key resource for small parties. Parliamentary entrance signals
organizational capacity and candidates’ appeal, and reduces uncertainty
about parties’ ideological profile. Taking advantage of the discontinuities
generated by thresholds of representation, we estimate the causal effect of
entering parliament on the future vote shares of small parties. We use a new
data set that covers all post-WWII democracies with a national threshold of
representation. Results indicate that presence in parliament increases
parties’ vote share in the next election. Importantly, entering parliament
is more important for parties in new democracies, where party branding is
weak and the need for signaling is high.