Issue congruence between candidates' Twitter communication and constituencies in an MMES: Migration as an exemplary case

How responsive are individual politicians to their constituents’ issue priorities? While parties compete nationally, candidates must navigate varying local issue salience. We investigate whether candidates adjust their emphasis on migration to district-level priorities in Germany’s mixed-member electoral system. Using survey data on voter issue salience and over a million candidate tweets from the 2017 Bundestag election, we apply supervised classification to assess issue congruence. Our findings reveal that MPs elected by their district are significantly more responsive to their constituents’ migration concerns than candidates elected via party lists. However, overall, candidates do not systematically align their communication with district-level preferences, suggesting that party strategies and electoral incentives shape responsiveness. These results underscore the role of electoral mandates in structuring political representation, highlighting the varying degrees of accountability in mixed-member systems.