Campaign spending limits are common in democracies worldwide, yet their electoral consequences remain unclear. Using unique data on over 70,000 UK parliamentary candidates from 1885 to 2019—detailing individual campaign expenditures and allocations—this study examines the impact of legal constraints on elections.

Data & Methods

Leveraging reform-induced variation in spending caps across constituencies, this research employs large-scale quantitative analysis. It tracks changes in: Campaign costs overall; Ad spending specifically; Candidate pool composition over time; Incumbency effects through different eras;

Key Findings

* Permitted spending increases primarily drive up ad-related campaign costs.

* Higher limits lead to fewer candidates, especially Labour ones, shrinking the field without boosting competitiveness.

* The election advantage for sitting MPs grows stronger as spending caps rise.

Why This Matters

These findings demonstrate a significant tension between campaign finance regulations and electoral competition in the UK. Spending limits favor established candidates by raising barriers to entry (particularly for Labour) while increasing incumbents' financial edge.