Given the general congressional uneasiness about the MX missile, the Senate's approval of funds for testing of the controversial weapon is primarily a political vote - not a military decision. In the wake of that vote, the question arises: Who won? Is President Reagan skillfully maneuvering the Congress into acceptance of the MX with a generalized promise to pursue arms control which does not bind him to early action but allows him to go forward with a weapon system he has always wanted? Or is the Congress wisely buying the President's ''package deal'' in order to build bipartisan pressure on the administration and actually achieve arms control?
The American public will hope the latter. But this does not rule out a more fundamental question: With MX in the picture, is arms control even possible? Many experts think not.
President Reagan demonstrated his considerable political talents in bringing the senators around to lifing the funding freeze on the MX. This was one of the most intensive lobbying efforts ever made to persuade lawmakers that Mr. Reagan is in earnest about arms control. No doubt the President was able to capitalize on what seems to be congressional relief that he has backed away from the ''dense pack'' basing mode for the MX and is at least pursuing a new approach to the problem of so-called ICBM vulnerability - namely, development of a new mobile, single-warhead missile. Certainly there is a yearning for bipartisanship and national consensus which the general public shares. To this extent, the government is moving in the right direction.
Yet misgivings remain which ought to warn against settling for a ''lesser of two evils.'' Even though he voted for the resolution, Democrat Sam Nunn, a defense expert, conceded that the MX is inconsistent with moving to smaller nuclear weapons. ''I still don't like it,'' he said of the new basing plan. Republican senator Nancy Kassebaum made clear that the Senate resolution on flight testing was designed to keep the administration's feet to the fire on arms control. Mark Hatfield, one of six Republicans who did not vote for it, went so far as to call arms control ''a mutilated term,'' while Democratic senator Alan Cranston dubbed use of the MX as a goad to arms control ''a cruel hoax.''
It will be a long time, of course, before the MX is actually produced and deployed. Even funding for its development must still run the gauntlet of debate and approval in the House of Representatives. At each stage of the legislative process there will be a chance to examine the wisdom of going down what so many believe is a futile path. Indeed it is hard to see any virtue in the MX, which is a destabilizing first-strike weapon, which would be put into Minuteman silos acknowledged by a presidential commission to be vulnerable to Soviet attack, which would force the Russians to respond with some new military development, and which would therefore escalate the arms race. Such a ''bargaining chip'' approach to arms control is highly dangerous, not to mention costly.
President Reagan can help dispel the deep concerns lingering in the Congress and among the public at large by providing solid evidence that he seeks to make arms control a reality. His words are reassuring. But the impasse in the strategic arms talks in Geneva, combined with the absence of firm arms control leadership in the administration, does not give confidence of serious negotiation. The need now is to show progress. There are reports that the administration plans to make significant changes in its proposals when the next round of START talks resumes in early June. This will be an early opportunity to demonstrate presidential commitment to arms control - in deeds as well as words.