How does an increase in the size of the electorate affect the use of violence during election campaigns? On the one hand, expanding the electorate might reduce violence by enabling citizens to vote rather than having to engage in contentious forms of politics. On the other hand, expanding the electorate increases its heterogeneity, which undermines clientelist networks and increases the total costs of bribery, making violence relatively more attractive. We investigate this theoretical puzzle in the context of the British Second Reform Act, which extended the franchise to the unskilled urban population in 1867 and thereby significantly increased the electorate in borough constituencies. Exploiting the sharp change in the size of the electorate, we isolate the effect of franchise extension from underlying constituency level traits correlated with the voting population, enabling us to get a better-identified estimate of the causal effect of franchise extension on election violence. Using an original dataset on election-related violent events in each parliamentary constituency at each general election between 1859 and 1880, drawn from historical newspaper and parliamentary committee reports, we find that the reform resulted in an increase rather than a decrease in electoral violence in the subsequent election. Looking at the subsequent two general elections, we observe that this increase in violence is sustained, suggesting that franchise extension has contributed to a new more violent electoral equilibrium. Our findings contribute to debates within the electoral violence, democratization, and the electoral reform literature.