The formation of a European public sphere (EPS) is a longstanding challenge in EU studies, particularly amid rising polarisation and the growing influence of radical-right parties. This study examines whether national political parties contribute to transnational discourse during the 2024 European Parliament elections or remain primarily guided by domestic competition. Using an original dataset of social media messages from European
Political Groups (EPGs), national parties, and candidates, we apply multilingual Sentence-BERT embeddings to measure semantic alignment between national actors and their European counterparts. Our findings reveal that domestic party system fragmentation and internal ideological dissent drive parties to prioritize intra-national coordination, increasing alignment with national peers while diverging from the EPG center. Conversely, national
parties often converge rhetorically with co-national peers, highlighting the layered dynamics of Europeanization. These results underscore the contingent nature of supranational party cohesion and the challenges of fostering a truly European public sphere, with implications for democratic accountability, public deliberation, and the future of European integration.