In the 2000s and 2010s, US states have seen an important wave of change in criminal justice policies toward a "smart on crime" approach. In this context, several states have rolled out algorithmic risk assessment tools for statewide use in pretrial decisions, whereas some others have not, and still others are moving back from using such tools again. The present article examines the explanations for this variance. To this end, it tests competing expectations about the role of functional pressures, including fiscal strain and the party-political balance of power. The findings show that functional pressures, policy diffusion, and politics affect the likelihood that algorithmic tools will be used in criminal justice. Democratic control of both the state executive and legislative branches increases the likelihood that a state will use these tools, indicating that Republicans are reluctant to leave the "tough on crime" paradigm behind and to advance the "smart on crime" approach.