We investigate the relationship between controversial roll call votes and support for Democratic incumbents in the 2010 midterm elections. Consistent with previous analyses, we find that supporters of health care reform paid a significant price at the polls. We go beyond these analyses by identifying a mechanism for this apparent effect: constituents perceived incumbents who supported health care reform as more ideologically distant (in this case, more liberal), which in turn was associated with lower support for those incumbents. Our analyses show that this perceived ideological difference mediates most of the apparent impact of support for health care reform on both individual-level vote choice and aggregate-level vote share. We conclude by simulating counterfactuals that suggest health care reform may have cost Democrats their House majority.