Do social influencers affect election outcomes? Social influencers can reach millions of people through social media platforms such as Facebook, YouTube and Instagram. However, research on social influencers is scarce and so far largely limited to marketing research. I argue that social influencers can influence elections through their role as digital opinion leaders and their power to shape the media agenda. Empirically, I will leverage an event that occurred during the 2019 European election campaign. Eight days before the 2019 EP election, the German social influencer Rezo published a video in which he severely attacks the governing party that was watched by over 11.5 million users until the election. I will identify the causal effect of this video on the election outcome by relying on a differences-in-differences design. The results of this study have major implications for our understanding of the relationship between social media, electoral competition and political representation.