After a bad week for the Center administration's SALT-selling campaign, senior government officials must contemplate the possibility that they have lost control over the debate on the new strategic arms agreement.

The prospects of a clean, up-or-down vote on the strategic arms limitation treaty [SALT II] as signed in Vienna two weeks ago are increasingly remote. Important senators whose support seems crucial if President Carter is to get his treaty appear determined to change the document significantly. Even sentators who are inclined to vote for SALT talk of changing it first.

For months the administration has hoped that, once published, the SALT treaty would become increasingly attractive to the Senate, and the idea of rejecting it would become increasingly implausible.

Sen. Howard H. Baker Jr. [R-Tenn.], the minority leader and a man on whom the White House has long counted for support, shattered that optimistic vision last week.

In his news conference Wednesday, Baker announced, in effect, that he was prepared to take one of two big risks: either to force the Soviets to renegotiate portions of SALT II, or eventually to retreat from the strong positions he took last Wednesday.

If Baker's gamble fails, his presidential compaign is likely to do so also. Some in the Carter administration say he has made a grave political error.

These officials are counting on the Senate to realize, sometime this summer or fall, that SALT is not a bad deal, and that reopening the negotiations now would be dangerous, would require new American concessions and would not guarantee and improved treaty.

The trouble with this argument is that it has been around for a long time, but it has failed to take hold. Through administration officials can describe how they will eventually take control of the SALT debate, they have thus far failed to do so.

In fact, the opponents of SALT II have been far more effective than the president and his colleagues in the struggle for senators' minds.

The opponents' success is a considerable achievement, given the virtually universal political assessment that the public is sympathetic to SALT II, even if poorly informed.

Carter had a personal opportunity to sway Baker last week, when the two met privately at the White House. But Baker was apparently offended by that meeting, leaving with the impression that Carter was insensitive to the Senate's desire to put its own mark on SALT II. Carter told Baker he would not accept substantial changes in the agreement.

Several administration officials expressed dismay last week that Baker based his major criticism of the SALT II pact on an argument that they believe is gravely flawed. The argument was that by allowing the Soviet Union to keep its force of 308 extra-large "heavy" missiles, the treaty gives the Solvets strategic superiority and will force the United States to spend many billions on a new MX missile.

Administration officials note that the 308 heavy missiles have been in the Soviet arsenal since the SALT process began, that former presidents Nixon and Ford both negotiated agreements allowing them to exist, and that Baker approved both of those agreements.

These officials deny that the extra payload capacity these rockets provide amounts to a significant strategic advantage. They note that SALT II substantially limits their military potential.

Administration sources also reject Baker's contention that the Soviet heavy missiles create a need for the MX. That need arises out of the theoretical vulnerability of America's 1,054 land-based missiles to a Soviet sneak attack.

This theoretical vulnerability exists once the Soviets have 2,500 to 3,000 warheads on their own land-based missiles. The Soviets could easily achieve this number of warheads even if they dismantled all their heavy missiles and replaced them with other rockets in their present force.

This is an arcane but potentially important point, one made forcefully by middle-level administration experts in provate conversation. But senior officials, beginning with the president, have left discussions of such issues to their underlings, and have not forcefully carried the case for the SALT treaty to the Senate.

The administration and its friends argue that these are early days in the SALT debate, that Carter and others will rise to the occasion later and that the treaty will ultimately win twothirds approval. This is certainly possible, but the record over two years suggests that optimism now requires a good deal of faith.

Two popular ideas in the Senate pose grave dangers to the White House. One is the feeling that the combination of SALT II and current American defense programs is insufficient to assure genuine strategic parity between the United States and the U.S.S.R. Baker made this argument last week.

The second idea is that SALT II simply isn't adequate, that it provides a license for more arms race rather than significant limits on the superpowers. Hard-line critic Sen. E. J. [Jake] Garn [R-Utah] take this view, as do Senate doves like Mark O. Hatfield [R-ore.] and George McGovern [D-S.D.] and many others.

Either of these concerns, or a combination of both, could derail SALT II in the Senate. On the other hand, both of them might be satisfied in a way that would also preserve SALT II.

This would be some Senate action that would bind both the United States and the Soviet Union to explicit goals for SALT III. For example, the Senate might amend the general principles now in SALT II that are meant to guide negotiation of the next agreement with very specific demands for substantial reductions of both superpowers' arsenals.

This is an idea that may attract increasing attention in the weeks ahead. Already, some administration officials have begun to think about it. But the path from here to there looks long and complicated.

What now seems certain is that the signing ceremony in Vienna did not end the SALT II negotiating process. The Carter administration will be negotiating throughout the summer and fall with the Senate and in the end perhaps with the Soviets again too.