Through the 1973 Roe v. Wade decision, the 1857 Dred Scott case, and back to the beginning of the republic, Supreme Court politics have mattered more than it’s been quite polite to acknowledge. The notion that justices rule always strictly on law rather than by reference to their political leanings has been a genteel fiction. The myth of purity has never been more utterly exploded than it is today.

Riddled with hypocrisy, the matter arises again because Justice Samuel Alito was hospitalized last month, and Democrats have a shot at winning the Senate in November’s elections. If a court vacancy opens this summer, President Donald Trump could nominate a conservative, and the Republican majority in the Senate could confirm him or her before voters cast their ballots. But if Democrats take power, they will block any Trump nominee. They promise this.