Primary Meddling Pays Off for Democrats

Democrats had a stronger Election Night than many analysts anticipated, buoyed in part by Trump-endorsed Republican candidates who performed worse than expected. But in six instances—three gubernatorial races, two House races, and one Senate race—Democrats actually participated in the process of selecting those Republican candidates by spending money in their primary campaigns. This cynical bet paid off.

Meddling of this nature isn’t unprecedented—in 2012, for instance, Missouri Democratic Sen. Claire McCaskill’s campaign boosted Todd Akin in the Republican primary before beating him in the general election. But many of the...