Why new parties?

The variables explaining party system fragmentation have been investigated extensively, but little is known about changes in the number of parties over time within countries. This article is an attempt to fill the gap by explaining the entry of new viable competitors in party systems after the founding election. Using empirical evidence from Spain, we show that when there is an electoral market failure and a high number of perfectly elastic voters, there is a high probability of new viable entrants. [ABSTRACT FROM PUBLISHER]