Mirror Politics: Two-Level Foreign Interference and Enlargement Contestation in Central Europe

The European Union’s enlargement policy is no longer a quiet technocratic exercise but a deeply geopolitical arena. This article develops the concept of two-level interference to explain how foreign actors contest EU enlargement both in candidate states (e.g. Serbia, Ukraine) and in member states (e.g. Slovakia, Hungary, Czechia). I argue that enlargement contestation is best understood as a form of mirror politics: when external actors project influence into candidate countries and cultivate sympathetic elites within member states, they create a reinforcing loop. This loop allows interference to penetrate the EU’s unanimity-based decision-making and obstruct, dilute, or reshape enlargement policy. The argument is developed through a most-similar systems comparison of Czechia and Slovakia. Both share post-communist legacies, entered the EU and NATO in 2004, and face similar exposure to Russian and Chinese influence. Yet their trajectories diverge. Czechia has consistently acted as a resilience case: supporting enlargement to the Western Balkans (including Serbia) on the basis of conditionality and democratic standards, and strongly advocating Ukraine’s EU candidacy as a geopolitical imperative. Czech governments have invested in counter-disinformation, expelled Russian diplomats, and cultivated elite consensus that prevents foreign narratives from shaping EU-level behaviour. Slovakia, by contrast, illustrates susceptibility: under Robert Fico’s leadership, Kremlin-aligned narratives have entered mainstream discourse, from portraying Ukraine as unfit for EU membership to downplaying Serbia’s democratic shortcomings. Here, Russian influence originating in Moscow and anchored in Belgrade finds a mirror in Bratislava’s domestic politics, reinforcing enlargement contestation at the EU level. By contrast, in Czechia the mirror remains broken: external narratives fail to gain domestic uptake and thus cannot translate into EU vetoes or dilutions. Our empirical evidence traces enlargement debates between 2022 and 2024, drawing on Council records, parliamentary debates, media discourse, and disinformation monitoring. It demonstrates how Moscow’s strategic interference, channelled through Serbia and Ukraine as candidate states, is variably reflected by member states: Slovakia acts as an amplifier, while Czechia resists, thereby showing how domestic institutions thereby showing how domestic institutions and political leadership mediate external influence. The central methodological approach is a most-similar systems design (MSSD), comparing Czechia and Slovakia. Both states share structural similarities: they were part of the same federal state until 1993, acceded to the European Union and NATO simultaneously in 2004, and occupy comparable geopolitical positions as small Central European member states bordering Ukraine. Both have been exposed to Russian and Chinese influence campaigns, and both wield equal veto power in EU enlargement decisions. Yet they diverge significantly in their political responses: Czechia has consistently backed enlargement to the Western Balkans and Ukraine, whereas Slovakia, particularly under Robert Fico’s leadership, has mainstreamed Kremlin-aligned narratives and adopted a more ambivalent stance. This divergence under conditions of similarity provides strong leverage for isolating the role of domestic mediation of foreign interference. Additionally, a discourse analysis of political and media narratives traces the circulation of Kremlin-aligned frames on Serbia and Ukraine.