This article analyses the impact of electoral institutions on the re-election campaigning and outreach strategies of Members of the European Parliament on the Twitter social media platform. Social media offers politicians a means to contact voters remotely and at low cost. We test the effect of diverse national proportional representation electoral institutions in European elections on a possible online electoral connection. We draw upon an original dataset of Members of the European Parliament Twitter activity before, during, and after the 2014 European elections. Our results confirm that variation in electoral institutions leads to meaningful differentiation in representatives' social media campaigning, which is further affected by national party, voter and legislator characteristics. Representatives make constructive use of Twitter, but there is no sustained online electoral connection.