How do the American people feel about that cluster of issues that surrounds SALT? According to poll results, the public seems to be stressing two big ideas. Both of them make sense.

First, in general, Americans have in recent months favored the idea of nuclear arms limitation. They want peace. They'd like to make a deal with the Soviet Union. However, as more specifics of this treaty, SALT II, have surfaced, support has diminished substantially. The last Gallup poll of the "informed" public showed that the "favorable" ratings have declined from 3 to 1 down to 5 to 3. Roper surveys tend to confirm both the approval and the declining direction of opinion on this matter. The NBC/AP survey, which has the latest data avaialble, shows support for SALT to be even-steven at best, after earlier polls had indicated solid favorability.

Second, the American people are fed up with the perception of American weakness around the world. This feeling has been growing for a number of years. It was solidified earlier this year as the Iran-Afghanistan-Mexico-Taiwan bombshells burst and the newsmagazines headlined "America in Retreat." Americans, the polls tell us, don't want to be "number two" to anyone and they want a stronger defense budget. They don't trust the Russians. They don't like being poorMouthed in the United Nations and they certainly didn't like being poor-mouthed by their own U.N. ambassador. Like Rodney Dangerfield, they'd like some respect.

Well, then, Ro-arms limitation and pro-toughness. But these are only general views by a non-expert public.

Asking a poll "respondent" whether he or she is "in favor" of the SALT treaty is about like asking the same respondent whether he believes that Einstein's Theory of Relativity is accurate. Does this respondent, after all, know very much about throw-weights, counterforce, Backfire bombers, hardened silos, "slickums" (sea-launched cruise missiles), "glickums" (ground-launched cruise missiles) or "creepy crawlies" (underwater mobile missile launching platforms)? No indeed, he does not know much, and his legislator knows he does not know much.

What happens, then, when these general views are heard and appraised by more expert legislators? How are they shaped on the political anvil?

Rather neatly it seems.

Not for the first time, and not for the last, the U.S. Senate is behaving in a very responsive way. Consider: How would one go about favoring the general idea of SALT and also the general idea of getting tough and turning around American foreign and defense policy? There is a one-word answer to that question: "linkage."

And so it has happened. Senators are demanding a variety of linking actions by either the Soviet Union or our own government. These linkages are designed to serve as an earnest that detente, capped by a SALT treaty, will not continue to be the proverbial "one-way street." That, by the way, is a thoroughfare that quite properly surfaces on political road maps every four years as the presidential election season draws upon us.

As so often happens in American political life, a symbolic event arrives like clockwork to join the issue. Today it is the appearance of the Soviet combat brigade in Cuba. Not terribly important in itself, the troop of 3,000 Russian soldiers has rightly become an important symbol. Get them out of there, say the senators -- both echoing and agreeing with their tough-minded constituents -- or we won't vote on your SALT treaty. One can properly speculate that even a symbolic response by the Soviets on the Cuban brigade may not be enough. The senators may well want further evidence that the Soviets will not continue down the road of political or military expansion.

The senators are demanding linkage from our own government as well. Urged by Sen. Sam Nunn, legitimized by Henry Kissinger, bolstered by Sen. Henry Jackson, the demand now is for an on-going 5-percent-per-year increase in adjusted-for-inflation defense spending. Guarantee to us, say the senators, that the Soviets will not become the number one military superpower, or we won't consider your SALT treaty. Last week the Senate voted by 55 to 42 to permit a 5 percent real increase in defense spending. At a time when inflation is the number one issue, and government spending a major irritant, that was indeed a remarkable vote.

One may properly ask whether the SALT II treaty is the proper vehicle to which to hitch these cosmic demands. No, say SALT defenders. SALT is good in its own right. Let's ratify it on its own merits. On a separate track we can then consider what our correct posture should be toward the Soviets.

There is a certain apparent logic to that position. Its proper rebuttal is that global politics, like domestic politics, need not always follow along the lines of readily apparent logic. SALT may not be the ideal trolley car to board in order to pursue other demands. But it happens to be the only trolley car coming down the track right now. Turning around a decade-long policy of American weakness (say these senators) requires a major act of political symbolism. It can't easily be done otherwise. And so they demand linkage. And it looks as if they will get it, or get some of it anyway, before they will vote on SALT.

The president's SALT-SELLERS have one major obstacle before them on the way to a treaty. Even if the Soviets respond, even if the Senate is satisfied on defense spending demands, the treaty will then have to be considered on its own merits. Many experts for whom I have great respect say that on its merits the treaty is a bummer, that it speeds up the nuclear arms race rather than slowing it down, that we were out-bargained and so on.

That argument, of course, gets precisely into hardened silos, counterforce, glickums, slickums and creepy crawlies. I am, I must confess, no better equipped to pass judgment on that argument than it the average poll respondent, which is to say hardly at all. Alas, our poor senators may ultimately be pushed to make such a technical judgment. Many of them, although more expert than their constituents, still don't know a great deal about slickums. They may have to learn. And no public opinion poll will be able to help them.