A diverse group of international scholars offers cutting-edge analysis of the Andrés Manuel López Obrador (AMLO) administration and Mexico’s “Fourth Transformation” – one of the most profound structural shifts in a major democracy, both within Latin America and globally. Chapters assess the complexity of this significant transformation in Mexican democracy and society. For decades, the political system operated through a dominant party and an entrenched ruling class, sustaining a hegemonic order. While the 2000 election broke the PRI’s hold, power remained concentrated without dispersing decisively. The subsequent center-right governments failed to provide better living standards, greater public security, or stronger institutional integrity. After two electoral defeats, AMLO’s victory in 2018 marked a rupture. As declared in his inaugural address, this was not merely a change of government but a regime shift – a new leadership, movement, and ruling class that reshaped ideology and governance alike. The volume explores key themes, from AMLO’s strategic ambivalence and leadership style to executive power, democratic institutions, and social policy implementation. It also traces the historical trajectory of the Morena movement, from its origins to its current struggle to navigate a pivotal leadership transition.