Political science literature tends to depict the role of ideas in policy in two distinct ways: ideas are seen as strategic tools mobilised by agents to achieve pre-given preferences; or as structures imposing constraints on what is considered legitimate or feasible. Discursive institutionalism seeks to combine these insights, suggesting that while actors are indeed constrained by deeply entrenched ideas, they nonetheless enjoy some autonomy in selecting and combining ideas. This article seeks to further develop this approach in two ways. First, we identify three discursive strategies through which policy actors can selectively mobilise ideas: they may foreground one level over others; exploit ambivalence in public philosophies; or link programme ideas over time by invoking ‘policy legacies’. Second, we elucidate the mechanisms through which such strategic selections can in turn modify existing public philosophies and programme ideas, thereby influencing policy change. We examine these claims by comparing discourse on immigration policy liberalisation in Germany and the UK between 2000-2008. We find evidence of all three discursive strategies. Moreover, we show how in the German case these discursive representations led to longer-term adjustments in underlying programme ideas and public philosophies on immigration.