SOMETHING ASTONISHING happened to President Reagan's strategic program the other day. The heart of it was quietly cut out by a Senate Armed Services subcommittee. This Republican-led panel, steered by John Warner (R-Va.) and Gary Hart (D--Colo.), voted 9 to 0 to put the proposed MX missile on the shelf until a basing method is found that is better than the questionable temporary method--shoving the MX into old, easily targeted Minuteman holes--that the administration had settled on last fall. But whether there is a better basing method has confounded strategic and political analysts for years. The MX may be dead.

This prospect is in the first instance a major embarrassment to President Reagan, whose principal line of attack on Jimmy Carter's defense policies was that he had allowed a "window of vulnerability" to open during which the Soviets could destroy the chief, land- based leg of the American deterrent. The Reagan MX scheme was meant to close at least part of that window. But this may be a lesser aspect of the subcommittee's decision. It has reopened all the great strategic issues precisely as the administration encounters growing turbulence over nuclear issues at home.

Since Mr. Reagan accepted local objections as a basis for abandoning the Carter MX deployment plan in Nevada and Utah, he cannot easily overrule local objections to deploying the missile elsewhere. The old options for hiding MX can be trotted out, and new exotic ones inspected, but that will be time-consuming and divisive. No less divisive would be a debate on protecting the MX by abandoning the 1972 Soviet-American treaty banning missile defense. The question is bound to stir up the controversy over whether, if the MX cannot be made survivable against a Soviet first strike, the country should have land-based missiles at all.

There is also the immediate matter of the forthcoming strategic arms control negotiations with Moscow. The Senate subcommittee, though it acted for other, understandable reasons, has taken off the table one of the major items Mr. Reagan meant to put on it.

The ultimate impact of shelving the MX, however, may be on the argument the country has been having over whether nuclear forces should be maintained strictly to deter war, or whether the United States must prepare actually to fight, survive and win a "limited" nuclear war. If you cannot maintain a responsive super-accurate missile force certain 1) to survive an enemy's first strike and 2) to let you retaliate against the targets of your choice, then how do you prepare for a "limited war"? You do not need to have accepted the idea of the possibility of such a limited war in the first place to see that the implications of this question are profound.

We suspect, in short, that the subcommittee's action is a real sleeper and that the country will be dealing with its consequences for years.