How to tamper with a Parliament: Strategic campaigns in apportionment elections

2026-01-22

Journal of computer and system sciences (Print)

AI Summary

This study investigates the computational complexity of manipulating election outcomes through limited voter mobilization—modeled as strategic campaigning or “bribery-style” attacks—in parliamentary systems featuring electoral thresholds and multiple districts. Employing both classical and parameterized complexity theory, complemented by large-scale experiments on real-world election data, the work systematically characterizes the intractability boundaries of this manipulation problem under several prominent seat allocation rules. It further introduces a novel “second-chance” voting mechanism designed to mitigate the exclusion of small parties due to threshold effects. Experimental results demonstrate that optimal manipulation strategies substantially outperform heuristic approaches, while the proposed mechanism proves both practically feasible and computationally tractable in realistic settings.

Technology Category

• Game Theory and Economic Paradigms: Social Choice / Voting
• Multiagent Systems: Mechanism Design
• Humans and AI: Voting

Application Category

• User Modeling, Personalization and Recommendation: Attacks and countermeasures in recommendation systems
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Problem

• apportionment elections
• strategic campaigns
• electoral manipulation
• computational complexity
• voter bribery

Innovation

• strategic campaigns
• apportionment elections
• computational complexity
• electoral threshold
• second-chance voting