Senate Minority Leader Chuck Schumer’s verbal threats against two Supreme Court justices aren’t surprising, in light of three years of “resistance” hostility to Trump judicial picks. What is remarkable is that Democratic leaders continue to take such a losing approach to an issue that will be central to the 2020 election.

Mr. Schumer did hit a new low Wednesday, when he stood outside the Supreme Court and rallied a mob of abortion-rights activists by vowing that Justices Brett Kavanaugh and Neil Gorsuch would “pay the price”...