The present study seeks to propose Habermas's (1976, 1992, 1998, 2001) validity-theoretic approach as a method for conducting political interdiscursive analysis. The approach is predicated on the methodological correlation between the three validity claims of truth, truthfulness, and rightness, on the one hand, and the respective speech acts of constatives, expressives, and regulatives, on the other. The data used for analysis is the resignation speech delivered by the ex-Prime Minister of the UK, Theresa May, on 24 May 2019 in Downing Street, following her political failure to deliver Brexit. The study derives its significance from attempting to uncover the pragma-argumentatively motivated interdiscursive patterns in May's speech. In other words, the explanatory power of traditional interdiscursivity can be enhanced through integrating the pragma-argumentative component of validity-claim theory into the current form of political interdiscursive analysis. The study's main finding is that, with the presence of pragmaargumentative links, there are four rationally oriented interdiscursive relations in May's speech: (a) practical-aesthetic, (b) practical-theoretical, (c) theoretical-aesthetic, and (d) aesthetictheoretical. Two crucial implications have emerged from this finding: (i) the dominant interdiscursive pattern in May's speech is the practical-aesthetic interdiscourse, where May justifies her validity claims to truthfulness through the normative context of what best serves the UK's political interests; (ii) both cases of theoretical-aesthetic and aesthetic-theoretical interdiscourses proved to have a dialectically interdiscursive meaning on the rational basis that two discourses are reciprocally justifyingand at some point, legitimatingeach other.