How to define political ads?

Online political advertising has grown significantly over the last few years. Currently, both policymakers and platforms are debating further restrictions on political advertising to deter misuse. This work investigates whether we can reliably distinguish political ads from non-political ads. Our results show a significant disagreement between what ad platforms, ordinary people, and advertisers consider political. We also proposed 3 metrics to assess the quality of political definition and evaluated the EU definition based on these metrics.