British MPs don't always follow party lines, even when ideology points toward strong discipline.

➡️ Data & Methods

* Original dataset of MP votes and speeches (1992-2015).

* New estimations of MPs' ideological positions within their party.

🔍 Key Findings

* Ideological extremity interacts with government control to trigger rebellion.

* Extremists are loyal in opposition but rebel more when their party governs.

* Rebel MPs emphasize their votes through speeches ('grandstanding').

🧬 Why It Matters

* Existing models of party discipline don't account for this pattern.

Rebellion strategy depends on both the MP's position within* the party and whether that party is governing or in opposition.