AbstractIn many political systems, legislators serve multiple principals who compete for their loyalty in legislative votes. This article explores the political conditions under which legislators choose between their competing principals in multilevel systems, with a focus on how election proximity shapes legislative behaviour across democratic arenas. Empirically, the effect of electoral cycles on national party delegations’ ‘collective disloyalty’ with their political groups in the European Parliament (EP) is analysed. It is argued that election proximity changes the time horizons, political incentives and risk perceptions of both delegations and their principals, ‘punctuating’ cost‐benefit calculations around defection as well as around controlling, sanctioning and accommodating. Under the shadow of elections, national delegations’ collective disloyalty with their transnational groups should, therefore, increase. Using a new dataset with roll‐call votes cast under legislative codecision by delegations between July 1999 and July 2014, the article shows that the proximity of planned national and European elections drives up disloyalty in the EP, particularly by delegations from member states with party‐centred electoral rules. The results also support a ‘politicisation’ effect: overall, delegations become more loyal over time, but the impact of election proximity as a driver of disloyalty is strongest in the latest parliament analysed (i.e., 2009–2014). Furthermore, disloyalty is more likely in votes on contested and salient legislation, and under conditions of Euroscepticism; by contrast, disloyalty is less likely in votes on codification files, when a delegation holds the rapporteurship and when the national party participates in government. The analysis sheds new light on electoral politics as a determinant of legislative choice under competing principals, and on the conditions under which politics ‘travels’ across democratic arenas in the European Union's multilevel polity.