The politicisation of European integration on politicians’ social media: which aspects of political opportunity structure matter?

European integration is often said to be politicised in punctuated bursts, yet evidence from Central and Eastern Europe (CEE) remains thin. We analyse EU issue salience in elite social media communication using nearly 200,000 tweets from party leaders in five CEE countries and Germany as a Western European benchmark (2007–2022). Combining content analysis with time-series cross-sectional models, we test how political opportunity structures and politicising moments shape EU salience. We find cyclical, event-driven dynamics: EU salience rises around European Parliament elections, EU-related referendums (with a distinct Brexit effect), and European Council summits, but declines before national elections. Council presidencies, Commission appointments, and the Eurozone and migration crises show no robust effects, and public Euroscepticism is not associated with EU salience. The study highlights how high-granularity, unmediated Twitter data capture short-lived fluctuations that lower-frequency sources miss.