Democrats have finally decided to make judicial nominations an election issue, after essentially ceding the ground to Republicans for decades. Hillary Clinton barely mentioned Merrick Garland or the Supreme Court vacancy on the stump; this time around Democrats are going all in. But forget the conventional play of highlighting policy areas where “Trump judges” differ from those a Democratic president would appoint: issues such as abortion, guns, affirmative action, voting rights, and campaign finance. This time, the Supreme Court itself is the target. With their eyes on 2020, Democrats are calling for the court to be fundamentally restructured: adding justices, changing the way they’re picked, and limiting how long they serve. After all, the “illegitimate” conservative majority — Neil Gorsuch “stole” Garland’s seat, while Brett Kavanaugh “is” a serial rapist who hid his work on...