Ever since Lazarsfeld and his colleagues’ (1944) seminal study, it has become common wisdom that election campaigns, if anything, serve the activation of voters’ fundamental predispositions. However, disagreement emerges on the role of partisan orientations. Although some authors consider them as fundamental predispositions, which are activated during the campaign and subsequently act as filters for incoming information, others argue that party attachments are simple running tallies of political assessments, which are constantly updated in response to campaign events, or decision shortcuts for voters innocent of substantial information. In this study, we scrutinize the role of partisan orientations in a direct-democratic campaign using data from a panel survey fielded during the run-up to the 2006 Swiss asylum law referendum. We find that, as voters accumulate knowledge in the course of the campaign, vote intentions dramatically converge on pre-campaign partisan orientations. Moreover, voters, whose earlier issue-specific and partisan orientations collide, tend to resolve their ambivalence in favour of their partisan leanings. These results corroborate the view of partisanship as a fundamental predisposition.