This article explores when radical parties gain electoral support.

* Previous studies identify the economy and mainstream party ideological shifts as key, but findings have been inconsistent.

* This research argues for an interactive model where anti-system voting is strongest under two simultaneous conditions: a weak economy AND significant ideological convergence among established parties.

Using data from multiple countries:

* Aggregate-level analysis shows a strong connection between negative economic performance and the emergence of mainstream party convergence, both factors fueling support for anti-system options.

* Voter-level studies reveal that perceptions of this establishment convergence intensify dissatisfaction with economic policies. Conversely, experiencing a weak economy makes people more receptive to radical alternatives if they perceive limited choice from established parties.

The findings suggest that when mainstream parties become too similar (converge) and the economy performs poorly, voter frustration is amplified and directed towards anti-system forces.