Abstract
Disguised parties are electorally competitive organisations that preserve a mainstream label while durably advancing radical-right projects through programmatic shifts, institutional engineering and ecosystemic capture. We theorise disguise as a strategic equilibrium that widens electoral appeal and reduces reputational and regulatory costs by separating audiences and sequencing illiberal change through low-visibility instruments. The concept differs from mainstreaming, rebranding and episodic hardening by requiring a sustained divergence between public self-placement and governing practice and by combining multiple channels over time. We develop a portable identification checklist and a threefold typology and apply them in a within-case, theory-guided process tracing of Fidesz (1989–2025). The case shows how mainstream signalling can shield radical-right governance: It legitimises legalistic institutional redesign, facilitates information-environment capture and raises the costs of alternation and rollback. From this logic we derive testable expectations about enabling conditions, especially radical-right competition, permissive oversight in media and judicial arenas, and party-finance loopholes, and about downstream effects on opposition coordination and policy feedback. The argument reframes democratic-backsliding debates by highlighting mainstream enablers as a distinct regulatory problem and by motivating ex ante, structural safeguards.