Linz defined authoritarian regimes by four qualities: limited, not responsible political pluralism; a legitimacy based on emotion and the regime as a 'necessary evil'; limited political mobilization; and vaguely defined executive power. Unlike totalitarianism, which seeks to transform society through a mobilizing ideology and a single mass party, authoritarianism tolerates some pluralism and relies on passive acceptance. Unlike democracy, it does not hold accountable elections. This distinction—developed in his 1975 chapter and 2000 book—became the standard framework for classifying non-democratic regimes.

In his influential 1990 article, Linz argued that presidential systems are less stable because they create a 'winner-take-all' logic where the losing candidate has no governing role. The fixed term of a directly elected president makes the executive unremovable even when unpopular, while 'dual legitimacy'—president and parliament both claiming democratic mandates—produces gridlock when they conflict. These rigidities make presidential democracies more prone to breakdown than parliamentary systems, where governments can be replaced through votes of no confidence.

Linz argued that democratic breakdowns are rarely caused by coup-makers or external enemies; instead, they result from the actions of democratically elected incumbents who subvert the rules from within. In his 1978 volume, he showed that most democratic collapses occur when the government itself—facing crisis, stalemate, or losing an election—chooses to bypass or suspend constitutional procedures. This 'self-inflicted' fragility means democratic survival depends less on external threats than on the commitment of political elites to democratic norms and institutions.

Linz and Stepan co-authored *The Breakdown of Democratic Regimes* (1978) and *Problems of Democratic Transition and Consolidation* (1996). In the latter, they updated Linz's original five-fold typology—democracy, totalitarianism, authoritarianism, post-totalitarianism, and sultanism—adding the crucial distinction between 'consolidated,' 'unconsolidated,' and 'transitional' democracies. Their joint work emphasized that democratic consolidation requires not just elections but also a functioning state, a civil society, and the rule of law.

Linz identified sultanism as a subtype of authoritarianism characterized by personalistic, lawless, and non-ideological rule, where the ruler treats the state as personal property and relies on fear and patronage rather than institutions or ideology. Unlike totalitarian or authoritarian regimes, sultanistic regimes lack even the pretense of legal-rational authority. Examples include Somoza's Nicaragua, Duvalier's Haiti, and, more recently, some post-Soviet polities. This concept, developed in *Totalitarian and Authoritarian Regimes* and *Sultanistic Regimes* (co-edited with Houchang Chehabi), remains a key tool for analyzing extreme personalist dictatorships.

A common misconception is that Linz's typology is merely descriptive and static. In fact, his framework was designed to analyze regime dynamics—how authoritarian regimes change, decay, or transition. He emphasized that authoritarian regimes are often 'intermediate' and can move toward democracy or toward more repressive forms. His later work with Stepan on democratic transitions explicitly examined how authoritarian breakdowns create opportunities for democratization. His typology was always a tool for understanding political change, not a simple classification system.

Linz's regime typology has been used to classify countries from Putin's Russia (often labeled 'hybrid' or 'electoral authoritarian') to Orbán's Hungary ('illiberal democracy'). His warning about presidentialism has been cited in constitutional debates in countries like Turkey, Brazil, and the United States. His analysis of democratic breakdown has been invoked to explain recent backsliding in Poland, India, and the Philippines. Linz's concepts remain the default vocabulary for understanding the authoritarian turn in global politics.