Referendums are frequently used to ratify European Union (EU)–related propositions. Since 1972 there have been in total 46 EU-related referendums, excluding third-country referendums on EU-related matters. While referendums are constitutionally mandated in some countries in order to ratify new treaties, other referendums are held for either normative or for political reasons.
Referendums deal with topics that are less familiar to voters, where key issues typically do not map onto domestic political cleavages. This means that we should expect that campaigns and the information they provide about the issues and the positions of political actors might matter more in framing issues than in first-order national elections. While there is by no means a scholarly consensus, recent research has shown, for instance, that an issue that dominates media coverage can impact how voters evaluate a proposition.
Finally, what do we know about voter behavior? While referendums on EU affairs have been criticized as being decided by “second-order” factors such as government popularity, there is evidence that when a proposition matters for voters, voting behavior is more dominated by issue-voting. Recent research has drawn on advances in cognitive psychology to investigate the impact of attitude strength and personality characteristics for voter behavior.