This article proposes a new analytical framework for the study of political careers in multi-level systems. It is argued that the study of vertical movements between political arenas, which constitutes the prevalent methodological approach in the literature on political careers, should be complemented by the study of horizontal movements within political arenas. Based on a longitudinal analysis of individual political careers, the micro-approach developed in this article allows the comprehension of all territorial dynamics of political careers in multi-level systems. Based on an in-depth case study of all 419 Walloon careers in Belgium, four career patterns are identified: national careers, regional careers, multi-level careers and discrete careers. Although Belgium presents an integrated structure of opportunity, it is demonstrated that key evidences underline the prevalence of a regional and a national political class along a highly integrated political elites.