At least 40 states have introduced legislation in 2019 aimed at reducing the cost of prescription drugs, according to LexisNexis State Net ’s legislative tracking system. Fifteen of those states have enacted such measures.

It’s the holiday season, and if most voters are thinking about politics at all they are probably pondering more about how to get through family festivities without a major blowup over differing political philosophies than they are about next year’s legislative agendas. But rest assured...