Summary This report classifies EU member states into three voter groups— "core" supporters , "doubters" , and "contrarians" —based on attitudes toward European integration, using data from Eurobarometer surveys, national election results, and academic research. The analysis quantifies the size of each group by country and assesses volatility in public opinion, identifying patterns linked to age, urban/rural divides, and economic conditions. Key findings include: "Core" supporters range from 25% to 60% across member states, with the highest concentrations in founding members (e.g., Germany, Ireland) and the lowest in Central and Eastern Europe (e.g., Poland, Hungary). "Contrarians" (hard Eurosceptics) now represent 10–55% of the electorate, with the highest shares in Poland, Hungary, and Italy. Volatility is low in Western Europe, medium in Southern Europe, and high in Central and Easter...