This paper examines how radical right party success impacts mainstream parties' policy positions.

Using a regression discontinuity approach, we address whether these positional changes reflect causal effects beyond public opinion.

Key Finding: The study demonstrates that radical right electoral success does influence mainstream parties' policies.

* Methodology: Leveraging exogenous variation from differing electoral thresholds allows for causal attribution of mainstream policy shifts to the presence and strength of radical right competitors, not just reflecting voter preferences.

* Scope: This effect is observed across different types of mainstream parties – both left-leaning and right-leaning ones appear to adjust their positions in response.

This work contributes significantly by highlighting that political competition involves active adjustments from multiple party actors.