Questions about the definition, meaning and limits of marriage have become a topic of fierce political debate in advanced Western democracies over the past decade as political leaders have sought to grapple with the issue of same-sex marriage. The rhetorical choices of leaders as they have made the case for or against moving away from traditional definitions of marriage have been central to shaping the national debate within different jurisdictions. This article applies the theoretical lens of ‘discursive institutionalism’ (Schmidt) and the analytical purchase of ‘rhetorical political analysis’ (Finlayson) to compare the rhetoric of Prime Minister David Cameron in the UK, Prime Minister Tony Abbott in Australia, and President Obama in the USA. We argue that Cameron and Obama have, in different ways, each sought to discursively re-define the institution of marriage by drawing on elements already endogenous to the institution itself.