Paxton proposed that fascism develops through five sequential stages: (1) creating fascist movements, (2) taking root as parties in a political system, (3) acquiring power, (4) exercising power, and (5) radicalization or entropy. He rejected static ideological definitions because fascism is a political practice that changes fundamentally as it moves through these phases. A movement in stage one shares little with a regime in stage five. His model emphasizes contingency: fascists rarely seize power alone but arrive through alliances with conservative elites. No single stage defines authentic fascism; the sequence as a whole distinguishes it from other political forms.

Paxton defined fascism as 'a form of political behavior marked by obsessive preoccupation with community decline, humiliation, or victimhood and by compensatory cults of unity, energy, and purity, in which a mass-based party of committed nationalist militants, working in uneasy but effective collaboration with traditional elites, abandons democratic liberties and pursues with redemptive violence and without ethical or legal restraints goals of internal cleansing and external expansion.' Unlike definitions centered on doctrine—like Roger Griffin's 'palingenetic ultranationalism'—Paxton's emphasizes what fascists do rather than what they say, and highlights the crucial role of collaboration with established elites.

No. Paxton argued that fascism was not supported by any coherent philosophical system and that its common ground belonged 'more to the realm of visceral feelings than reasoned propositions.' He identified a set of 'mobilizing passions'—the primacy of the group, belief in victimhood, dread of decline, the need for unity, the authority of natural leaders, and the beauty of violence—that formed the emotional lava of fascism. These passions, not intellectual programs, drove fascist politics. This position distinguished him from intellectual historians who treated fascist texts as serious philosophy. Paxton famously quoted an Italian fascist: 'The fist is the synthesis of our theory.'

Sternhell located fascism's origins in a pre-1914 intellectual synthesis of ultra-nationalism and revolutionary syndicalism; Paxton emphasized the post-war crisis and the primacy of action over ideas. Griffin defined fascism through the myth of national rebirth (palingenesis) and treated it as a coherent ideology; Paxton dismissed coherent ideology as central, focusing instead on behavior, stages, and elite collaboration. Paxton's functional definition and stage model were designed to accommodate the enormous variation among national fascisms—Italian, German, French, Spanish—without reducing them to a single doctrinal checklist. His approach is historical and comparative; theirs are more conceptual and typological.

Paxton was the first historian to establish, using captured German archives, that Vichy France actively collaborated with Hitler's Europe rather than merely being a passive puppet. His 1972 book Vichy France: Old Guard and New Order, 1940–1944 argued that Vichy's leaders pursued their own authoritarian project and sought a place in a German-dominated Europe. This finding was initially received coolly in France, where the myth of a resistant nation prevailed, but became widely accepted. With Michael Marrus, he extended the analysis in Vichy France and the Jews (1981), documenting Vichy's autonomous antisemitic policies and complicity in the Holocaust.

Paxton deliberately avoided using his model to label contemporary figures, but his framework provides tools for analysis. Most contemporary movements that draw fascist comparisons remain stuck in stage one or two—creating movements and perhaps taking root—without the elite collaboration and paramilitary mass mobilization that characterized historical fascism. Paxton emphasized that fascism comes to power through cooperation with conservative elites, not through electoral victory alone. He also warned against loose usage that equates authoritarianism with fascism, arguing that precision matters because the term describes a specific political process with identifiable stages, not a general mood of intolerance or a set of policy positions.

Some scholars argue that Paxton's five-stage model imposes a developmental logic on fascism that is too rigid and teleological—that it makes fascism appear as an inevitable unfolding rather than a contingent, messy historical process. Critics from a 'stagist' perspective contend that fascist movements do not necessarily progress neatly from one stage to the next, that entropy can occur at any point, and that the model risks reading history backward from the regimes that succeeded. Paxton himself acknowledged that no stage guarantees the next and that many movements fail to advance beyond early phases. The critique is less a rejection of his comparative method than a caution against treating the stages as deterministic law.