This article makes the case that feedback processes in democratic politics—between crime rates, public opinion, and public policy—can account for the growth of penal populism in Britain. It argues that the public recognize and respond to rising (and falling) levels of crime, and that in turn public support for being tough on crime is translated into patterns of imprisonment. This contributes to debates over the crime–opinion–policy connection, unpacking the dynamic processes by which these relationships unfold at the aggregate level. This uses the most extensive data set ever assembled on aggregate opinion on crime in Britain to construct a new over‐time measure of punitive attitudes. The analysis first tests the thermostatic responsiveness of punitive attitudes to changes in recorded crime rates as well as self‐reported victimization, and then examines the degree to which changes in mass opinion impact on criminal justice policy.