Voting Decisions Under Compressed Timelines: How Snap Election Calls and Campaign Dynamics Shape Vote Choices and Their Certainty

Snap election calls disrupt the expected electoral calendar and provide a unique opportunity to study how sudden political events shape voter decision-making. While prior research has causally demonstrated that snap election announcements reduce uncertainty in vote intentions, we know little about the durability of these effects, for whom they are strongest, and whether they affect vote choices on election day. We expand this work and argue that snap election calls act as informational shocks that accelerate voters’ engagement with the electoral context. Crucially, we hypothesize that the durability of these effects varies across the electorate and largely depends on political interest and partisanship as well as on coalition expectations and the viability of expected coalitions. To test this, we use high-frequency panel data from Germany (GLES) and the UK (BESIP), which allow us to track within-person changes in vote intention uncertainty and party choice over time. Applying survival analyses and individual-level fixed-effects models, we examine the duration, heterogeneity and electoral consequences of these effects. The results show that the uncertainty reduction is initially strong but short-lived for many voters, while for politically attentive partisans, it stabilizes and translates into sustained vote preferences. These findings refine our methodological understanding of temporal dynamics in event-driven electoral behavior.