Party primaries are increasingly used in advanced democracies to select party leaders and electoral candidates. However, the factors influencing a candidate’s win in such elections are still under-researched. This paper studies to what extent primary voters rally behind party elites’ preferred candidates by studying the electoral consequences of primary endorsements by party elites. Taking inspiration from the US-based literature, here is proposed that party elites, such as regional party leaders and members of parliament, can influence the result of primary elections through two different campaigning mechanisms. On the one hand, party elites can campaign in favor of one candidate in front of primary voters. Alternatively, party elites may support a candidate by bringing more voters to the polls. To analyze the electoral consequences of elite endorsements, this paper uses three nationwide primaries from the two main Spanish political parties since 2014, the conservative PP and the social democratic PSOE. Initial findings indicate that candidates endorsed by party elites tend to perform better due to a higher primary voter turnout in the areas where party elites actively support them.