IN MOVING to drop nearly 50,000 people-- most of them aged, blind and disabled--from its Medicaid rolls, Virginia has stepped out smartly in the race to turn back the clock on social progress. This action of the state health department is notable for reasons that go beyond the severe hardship it will inflict. It indicates what is likely to happen elsewhere as states and localities react to reduced federal aid, and it signals the new federal policy of condoning, even encouraging, cutbacks in state efforts as well.

The special fault here is not that Virginia will fail to make up the federal Medicaid money it will lose. It is that its own Medicaid cutback is almost four times larger than the federal loss. Virginia has decided to take advantage of the Reagan guidelines to save a bundle of its own money.

Many states have already sought to cut Medicaid costs by reducing non-essential services and limiting payments to health care providers. But bargaining with doctors and hospitals and other sorts of cost containment are not likely to produce the quick, large savings that Virginia wants. So the state has decided simply to stop coverage for a large group of current recipients and to cut out expensive kinds of care for many others.

The Virginians who will lose coverage--the so- called medically needy--generally have incomes somewhat above the welfare level, typically from Social Security, and have spent all their "excess income" on medical care but still need help. Nationally, people in the medically needy category account for one-fifth of the cases but almost half of Medicaid costs.

They are expensive because they are sick: chronically ill or expensively curable, with progressive debilitation, severe injury, terminal cancer or advanced senility. Some are children born with congenital deformities, perhaps treatable but at enormous cost.

In the old days, many of these people could not be helped. They saved the taxpayer money by dying quickly. Others lingered on in county almshouses and charity wards or by begging on the streets. The lucky ones were tended by relatives, though often at the cost of financial ruin or stunted lives for their not always willing caretakers.

No doubt many Virginia doctors and hospitals will still care for acutely sick patients who can't afford to pay. The uncovered costs will show up in higher medical insurance premiums for private care and higher local taxes for public care. People needing long-term care may not be so lucky. Perhaps they can find a place in already crowded county facilities or persuade a relative to take them in. Or they might find their way to another state with a less fragile sense of social commitment.

As federal aid declines, should state taxes be raised or should services be cut? One candidate for governor in Virginia, Marshall Coleman, flatly opposes any tax increase. The other, Chuck Robb, doesn't like raising taxes but retains some openness. That's a distinction Virginia voters should keep in mind next Tuesday.