The 2015 General Election (GE) marked the end of the two-party system that had existed in Spain since the restoration of democracy. Two new parties, ‘Podemos’ and ‘Ciudadanos’ entered the national arena for the first time and together obtained 34.6 percent of the vote. This paper describes this election's context and electoral results by analysing the individual determinants behind the change to the Spanish party system. Our results indicate that economic factors predominantly explain the votes for the traditional parties, the PP and PSOE. On the other hand, political factors help distinguish why some voters remained ‘loyal’ to the traditional parties and others switched to the new formations. While Podemos’ switchers were mainly politically disaffected left-wing voters, electoral support for Ciudadanos came from younger and ideologically moderate voters who had lower levels of political trust.