Discovering Hidden Subelections

We show how hidden interesting subelections can be discovered in ordinal elections. More precisely, we address the problem of finding large sets of voters who have a consistent opinion regarding a large set of candidates, focusing on three interpretations of consistency: Identity (voters have the same rankings), antagonism (half of voters shares a ranking of candidates, while the other half ranks them in the reverse order), and clones (all selected voters rank all selected candidates contiguously in the original election). We first provide theoretical results concerning the computational complexity of our problem. Then, we report an experimental study on identifying consistent subelections, both on synthetic and real-life data.