Are electorally vulnerable politicians really less likely to support controversial legislation, such as pension reforms? While the literature on welfare state retrenchment has increasingly pointed to the role of electoral factors in the dynamics of social policy cutbacks, there are few studies that actually measure the magnitude of electoral pressure and its consequent impact on the politics of reform. To this end, the authors have developed a quantitative measure of the electoral vulnerability of politicians and tested its impact on pension reform outcomes using an original dataset comprising 16 Western European countries from 1980 to 2003. In line with expectations, the results show that the impact of electoral vulnerability on reform depends upon the system of interest intermediation. In corporatist systems, electoral vulnerability indeed impedes reform. But in pluralist systems, increased electoral vulnerability is associated with higher levels of reform. This is because unions in corporatist (but not in pluralist) systems can exploit electoral vulnerability in pre-legislative bargaining, and thus pressure politicians. Consequently, this study has broader implications for the differential responsiveness of democracies to redistributive issues more generally.