Voting is often said to be irrational because of the incredibly small likelihood that an individual voter’s ballot will be pivotal in favour of her preferred candidate or party. A persuasive response to this is to think of voting in terms of a ‘contributory causation’: a single voter can accordingly cause an outcome by being part of the set of votes that is decisive in bringing that outcome about. This article applies this theory of voting to European Parliament elections, arguing that European Parliament elections create especially high epistemic barriers to this sort of voting. Due to how European Parliament elections are organised, voters can barely know if and when their vote can be causally efficacious. The article concludes by suggesting that genuinely transnational political parties can go a long way in overcoming this problem, since they considerably simplify the electoral contest.