Building on an interdisciplinary approach bringing together political science and linguistics, this paper investigates how and why metaphors are used by Belgian politicians. In particular, the article focuses on the usage of metaphors to describe the evolution of federalism in the country over time. As argued by Ritchie (2013), ‘examining metaphors that appear in political discourse provides insights into the way speakers understand their situation, and how they seek to accomplish their ends’. This research undertakes a systematic analysis of the use of metaphors by Belgian politicians during television debates from the 1980’s until now. We rely on an original longitudinal corpus of 127 (part of) television debates covering 40 years from both public broadcasters in Belgium: the Dutch-speaking VRT and the French-speaking RTBF. The selected television debates relate to the progressive – albeit not without political tensions – transformation of Belgium’s political system. Our corpus is thus a solid indicator of this political transformation and therefore provides a fertile ground for the analysis of metaphors. To do so, we will conduct a corpus analysis by applying the MIPVU procedure (Steen et al., 2010) in order to identify potential metaphorical contexts. In line with Steen’s three-dimensional model (2008), we will subsequently analyse the identified metaphors by making a distinction between three different layers of metaphor, respectively at the linguistic, conceptual and communicative levels. Building on previous studies (Perrez & Reuchamps 2014), this analysis makes it possible to determine which (deliberate) metaphors have been used by the political elite to describe the establishment and evolution of the federal system, and more specifically, to assess to what extent this metaphor usage evolved over time and across the linguistic border.