Ann Math Artif Intell (2018) 82:219–244
Complexity of control by partitioning veto elections
and of control by adding candidates to plurality elections
Published online: 26 October 2017
© Springer International Publishing AG 2017
Abstract Control by partition refers to situations where an election chair seeks to influence
the outcome of an election by partitioning either the candidates or the voters into two groups,
thus creating two first-round subelections that determine who will take part in a final round.
The model of partition-of-voters control attacks is remotely related to “gerrymandering”
(maliciously resizing election districts). While the complexity of control by partition has
been studied thoroughly for many voting systems, there are no such results known for the
important veto voting system. We settle the complexity of control by partition for veto
in a broad variety of models. In addition, by giving a counterexample we observe that a
reduction from the literature (Chen et al. 2015) showing the parameterized complexity of
control by adding candidates to plurality elections, parameterized by the number of voters,
is technically flawed, and we show how this reduction can be adapted to make it correct.
Keywords Computational social choice · Voting · Veto election · Control complexity
Mathematics Subject Classification (2010) 91B14 · 68Q17 · 68Q15 · 68T99
Preliminary versions of this paper have been presented at the 14th International Symposium on
Artificial Intelligence and Mathematics (ISAIM 2016) and have appeared in the proceedings of the
22nd European Conference on Artificial Intelligence (ECAI 2016)  and of the 16th International
Conference on Autonomous Agents and Multiagent Systems (AAMAS 2017) . This paper
combines some of their results, unifies and simplifies their proofs, and adds discussion and examples.
ur Informatik, Heinrich-Heine-Universit