Subnational analyses of political preference are crucial for understanding policy dynamics and causal effects within the European Union. However, reliable estimates have been difficult due to a lack of adequate regional data sources. This paper leverages Eurobarometer survey data—a rich source typically designed for national-level insights—to address this gap.

Our approach involves comparing cutting-edge statistical techniques capable of generating representative regional predictions from nationally collected information. By validating these methods against independent regionally representative surveys, we identify significant challenges in achieving accurate subnational preference estimation using existing tools and methodologies.

Key Findings:

* Subnational analyses are essential for political science research.

* Estimating regional preferences accurately remains difficult despite available data.

* Validation with region-specific datasets is critical to assess accuracy.

We find that the most effective technique combines Bayesian additive regression trees (BART) with synthetic post-stratification. This hybrid approach significantly improves predictive validity when applied across European Union nations, enabling more nuanced understanding of regional political landscapes without requiring entirely new data collection efforts.