It is not true that the President threatens to make his daughter Postmaster General whenever she declines to eat spinach.

Still, the thought of heading (or even being linked with) the gigantic, controversial mail-moving corporation is enough to frighten bright children, and make even the boldest politicians run for cover.

The fear of being folded, stapled and mutilated by association with the U.S. Postal Service is a major reason the Senate will take its time next year before handing President Carter a "reformed" U.S. Postal Service. The USPS, its employees and those of us who get or send mail, face the prospect of a long, hot and maybe expensive summer. And people who love the President want to spare him as much postal-related grief as possible.

The problem is that the USPS, currently being reformed by the House, may suffer a strike, or a major stamp price increase, or both, by mid-summer.

The contract between the USPS and it big employee unions expires in July. August is when the unions have their conventions and, shortly thereafter, they elect officers.

The reform bill working its way through the House would give the President authority to pick the Postmaster General, and remove some of the insulation the service now has from Congress, the White House and Public Pressure. Insiders expect the House will approve the postal reform package early next year, but that they senators, partly to protect the President, will make sure its progress over there is slow.

The idea is to let the present management team stew in its own juices, and suffer whatever consequences that labor negotiations, internal and external politics and inflationary factors may bring.

Union leaders will be under tremendous pressure from members (and rivals for their jobs) to hang tough during negotiations. Matching the current three-year contract won't be easy. Among other things it provided the 600,000 rank-and-file employees with free-life insurance, four pay raises, six cost-of-living raises and a no-layoff pledge. Another one of those will make the 13-cent stamp a collector's item.

Negotiations for the new contract begin in April with everybody - unions, management, Congress and the public - involved and nervous. None of the most likely options - a fat, expensive contract or a strike - would do President Carter any good if he had the USPS under his wing. Better, it is thought, to let it carry on as a quasi-independent corporation until its summer troubles are over.

And that is why the Senate will take its time in reforming the postals service, and giving it back to the President. He will have a tough enough summer without that gift.

Housing and Urban Development has frozen most hiring and promotions because of a major field reorganization that is about to begin. HUD officials don't want to take on any new people, or get involved in promotions until the dust settles from the shakeup. It will involve many transfers, some demotions and layoffs.

Assistant Secretary for Administration William A. Medina is controlling the freeze, and exemptions to it.

National Treasury Employees Union says it has reached an impasse with the U.S. Customs Service. NTEU represents the [WORD ILLEGIBLE] headquarters employees here and has been bargaining with Customs officials for the past 18 months. The union broke off talks yesterday charging that management had "stalled and delayed and dodged any agreement in every conceivable manner." Customs brass say they are willing to continue talks, and deny any foot-dragging.