Referendums impose considerable informational demands on voters. Recent theoretical and empirical research has emphasized the different shortcuts and heuristics they may employ in deciding how to vote. Relying on a substantial series of votes at the national level in Switzerland, we provide empirical tests on how Swiss voters cope with the informational demands in referendum voting. We combine simple heuristics, like partisan cues and endorsements, with indicators of instrumental interests to explain citizens' choices in a series of votes.