Amid the carnage of Republican misrule in Washington, there is this glimmer of good news: The family-shredding policy along the southern border, the most telegenic recent example of misrule, clarified something. Occurring less than 140 days before elections that can reshape Congress, the policy has given independents and temperate Republicans — these are probably expanding and contracting cohorts, respectively — fresh if redundant evidence for the principle by which they should vote.

The principle: The congressional Republican caucuses must be substantially reduced. So substantially that their remnants, reduced to minorities, will be stripped of the Constitution’s Article I powers that they have been too invertebrate to use against the current wielder of Article II powers. They will then have leisure time to wonder why they worked so hard to achieve membership in a legislature whose unexercised muscles have atrophied because of people like them.

Consider the melancholy example of House Speaker Paul D. Ryan (Wis.), who wagered his dignity on the patently false proposition that it is possible to have sustained transactions with today’s president, this Vesuvius of mendacities, without being degraded.