STARTING IN August, the postman will no longer ring even once on Saturdays. Patrick R. Donahoe, postmaster general and chief executive of the U.S. Postal Service (USPS), says the move to five-day delivery — except for packages — will save the cash-strapped organization $2 billion per year. Praised by some postal reformers as a long-overdue cost-cutting move yet condemned by postal unions and rural lawmakers as a legally questionable abandonment of “universal service,” USPS’s announcement is actually a blend of “common sense,” as Mr. Donahoe said, and desperation.

Postal management has been begging Congress for years for explicit statutory authority to end Saturday delivery, arguing that it’s one of several structural reforms without which USPS cannot survive the digital age. The Postal Service’s financial plight is difficult indeed. Despite years of aggressive cost-cutting, it recorded a $15.9 billion loss in fiscal 2012, defaulted on $11.1 billion in retiree health-benefit prefunding payments and temporarily maxed out its $15 billion line of credit with the Treasury. Prior to Wednesday’s announcement, USPS forecast a $7.6 billion net loss in the current year.

Still, Congress, in its wisdom, has not legislated five-day delivery, or any other structural change, so USPS acted unilaterally Wednesday, exploiting what it says is a loophole in existing law.

The smart thing for Congress to do would be to let USPS’s action stand and take it as a cue to address the Postal Service’s chronic problems. Certainly comprehensive reform legislation would be a better use of everyone’s time between now and August than disputing USPS’s plausible but aggressive interpretation of the law.

Oceans of ink have been spilled debating whether the Postal Service’s crisis was inflicted by Congress’s decision to order more than $5 billion per year in health-benefit prepayments or by the inevitable consequence of technological obsolescence and high fixed costs, especially labor costs.

We tend toward the latter view. But even that does not quite express USPS’s true dysfunction, which is rooted in a convoluted, unworkable governance structure. Like Gulliver tied down by the Lilliputians, this supposedly independent, self-supporting entity answers to a presidentially appointed board, Congress, several labor unions and a regulatory commission — not to mention the demands of corporate mailers and, last but not least, the general public.

Each of the Postal Service’s various constituencies defends its piece of the action: Members of Congress protect redundant post offices as a source of jobs; unions enjoy a no-layoff clause and better health benefits than other federal workers; customers, corporate and individual, agitate for cheap rates. Of course, all of them think someone else should pay. Actually, the public is the most willing to sacrifice: Polls show overwhelming support for the elimination of Saturday delivery.

If you think the Postal Service is a case study in the special-interest gridlock that plagues U.S. government generally, we agree with you. That’s why reforming it, root and branch, is such an important test for Congress. So far, lawmakers have shown that they can’t, or won’t, do the job. We hope that, by precipitating the issue of Saturday delivery, USPS management will finally snap them out of it.