Staying in the First League: Parliamentary Representation and the Electoral Success of Small Parties

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.