Mexico's authoritarian dominant party regime is a curious hybrid.¹ The 1917 Constitution is an advanced liberal charter and some basic rules of political procedure ‐ such as the fixed timetable for federal elections and the no re‐election rule ‐ are strongly institutionalised. Yet for over 60 years the regime was also clearly authoritarian, deriving its legitimacy from the revolution rather than the electorate. This article analyses the sui generis nature of the Mexican authoritarian regime, tracing the way formal constitutional rules were supplemented (or displaced) by a coherent and relatively flexible set of informal understandings perpetuating one party dominance. It counterposes these country‐specific characteristics to comparative accounts of how authoritarian regimes ‘break down’, or introduce a ‘political liberalization’ which perhaps opens the way to a ‘transition’ to democracy. Under each of these headings Mexican reality demands significant adaptations to the standard account. During 1994 Mexico underwent severe upheavals without a ‘breakdown’ of the regime. Instead the 1994 presidential election provided a reasonably authentic electoral mandate to the current administration ‐ and yet the process of ‘transition’ to democracy in Mexico remains elusive. This article uses the current Mexican process to probe the scope and limitations of the comparative democratization literature.