EuroCon: Benchmarking Parliament Deliberation for Political Consensus Finding

Achieving political consensus is crucial yet challenging for the effective functioning of social governance. However, although frontier AI systems represented by large language models (LLMs) have developed rapidly in recent years, their capabilities on this scope are still understudied. In this paper, we introduce EuroCon, a novel benchmark constructed from 2,225 high-quality deliberation records of the European Parliament over 13 years, ranging from 2009 to 2022, to evaluate the ability of LLMs to reach political consensus among divergent party positions across diverse parliament settings. Specifically, EuroCon incorporates four factors to build each simulated parliament setting: specific political issues, political goals, participating parties, and power structures based on seat distribution. We also develop an evaluation framework for EuroCon to simulate real voting outcomes in different parliament settings, assessing whether LLM-generated resolutions meet predefined political goals. Our experimental results demonstrate that even state-of-the-art models remain undersatisfied with complex tasks like passing resolutions by a two-thirds majority and addressing security issues, while revealing some common strategies LLMs use to find consensus under different power structures, such as prioritizing the stance of the dominant party, highlighting EuroCon's promise as an effective platform for studying LLMs' ability to find political consensus.