Election manipulation with partial information

Abstract

We consider the case of manipulating the results of Instant Runoff Voting (IRV) elections. Previous work in this area looked at posthoc manipulation with complete information, where the manipulator may alter ballots after reading the whole election profile. In this paper we examine the much more realistic, but challenging, problem of manipulating ballots during the election process, having observed only some ballots. The aim of the manipulator is to modify as few ballots as possible to ensure their candidate’s victory with high probability. We show that this it quite feasible in practice to generate efficient manipulations with a high probability of success. We also add some extra conditions on the manipulations so it is less likely they will be detected by naive methods.