Do Your Job, Keep Your Seat: The Causal Effect of MPs' Legislation on Reelection

Distinguishing between personal and party votes is inherently challenging, and it remains unclear to what extent they function in each country. This study employs the ballot of a private member's bill as an instrumental variable to examine whether legislative behavior influences electoral outcomes in the United Kingdom, which has a highly institutionalized party system. The findings reveal that legislative behavior increases the vote share of Conservative MPs by 2.6 percentage points compared to the previous election. However, given the high prominence of the party vote, this increase is only large enough to change the electoral winner in just under 10% of the constituencies. Furthermore, for opposition MPs, legislative behavior had no effect in any respect. Nevertheless, this result suggests that personal votes exist even in an unlikely case—when party competition is intense and MPs have limited autonomy in Parliament.