LAST YEAR Senate Majority Leader Robert C. Byrd of West Virginia declared that the Panama Canal treaties negotiated by the Carter administration were doomed unless public opinion shifted decisively. He, like most others, thought voters overwhemingly opposed the treaties. Several polls, after all, had indicated that opposition was running as high as 10 to 1.

Then, earlier this year, prospects suddenly changed. The treaties appeared to have a chance. A Gallup Poll taken in early January found for the first time that more Americans supported the treaties than opposed them. A vast switch in attitudes appeared to have taken place.

No such thing. There had been a gradual change in sentiment, but certainly not a startling one. The fact is that American opinion had never been as massively against the treaties as thought. Nor does opposition, then or now, chiefly reflect a desire to assert American military might after the agonies of Vietnam and a perceived decline in American power. That Byrd and others believed part or all of this to be true, however, tell us something about polls and politics - or about how polls can distort politics - a lesson worth pondering as the Senate continues its heated debate over the treaties.

The Gallup Poll has never shown overwhelming opposition to the treaties. When Gallup first started asking about the canal last August, there was only a 7-point difference between supporters and opponents, with 46 per cent against and 36 per cent in favor. Two months later the difference was 8 points: 48 per cent opposed, 40 per cent favorable. And then in January, with the portion of Americans aware of the treaties having risen to 81 per cent, the plurality of 45 per cent to 42 per cent supported the pacts.

That is surely no sudden shift of attitudes. Why, then, the sharply different public, press and political perceptions? It should come as no great surprise to anyone by now that answers to polls depend on the questions asked, and a review of 25 poll questions on the canal by 10 organizations makes clear that, on this and other important points, the same holds for the Panama issue.

The most extreme majorities opposed to any change in the status of the canal were registered in polls taken by the Opinion Research Corp. of Princeton, N.J., before the signing of the treaties in September, 1977. ORC asked respondents, "Do you favor the United States continuing its ownership and control of the Panama Canal, or do you favor turning ownership and control of the Panama Canal over to the Republic of Panama?" The May, 1977, poll showed a vast 70-point margin in favor of American ownership and control: 78 per cent for U.S. control, 8 per cent for turning ownership and control over to Panama.

The point did not escape one of the leading opponents of the canal treaaties, Republican Sen. Jesse A. Helms of North Carolina, who cited the 78 per cent figure on "Meet the Press" in August, 1977, as evidence that a strong majority opposed the treaties. But of course the ORC question did not ask about the treaties. It did not even mention them.

It asked whether "ownership and control of the Panama Canal" should be turned over to the Republic of Panama. The alternative positions was "the United States continuing its ownership and control of the Panama Canal." Given such an extreme choice, and with no mention of the provisions of the actual treaty, there was no mistaking how Americans feel.

Much the same can be said for a question asked by NBC News and the Associated Press in October, 1977, just after the treaties had been signed: "The new treaty between the United States and Panama calls for the United States to turn over the canal to Panama at the end of this century. However, this treaty still has to be approved by the Senate. Do you favor or oppose approval of this treaty in its present form by the U.S. Senate?"

This poll, like the earlier ORC one, stated only one provision of the treaty - that it would require the United States to "turn over the canal to Panama," a rather imprecise description of the complex and ambiguous legal situation. Moreover, respondents were asked whether they favored of opposed Senate approval of the treaty "in its present form," which invited those who favored any modifications, however slight, to answer "no".

On the other hand, the NBC News/AP poll, unlike the ORC poll, explicitly referred to a treaty (actually, two treaties) and noted that the canal would not change status until the end of this century. It also put its question to the three-quarters of the sample who said that they had heard or read something about the treaties. These respondents were still strongly opposed, but by about a 2 to 1 margin, not the 10 to 1 of the ORC survey. "Control" Is the Key Word

A LOOK AT ALL the questions asked over the past year reveals that "control" of the canal has long been the key issue to the American public. Any question which specifies that the United States will hand over control of the canal to Panama elicits a strongly negative public reaction - unless the meaning of "control" is further qualified.

When three different polling organizations - the Associated Press, Louis Harris and the joint CBS News/New York Times survey - asked Americans about the treaties in September and October of 1977, their questions also focused on "relinquishing control" or "granting control" of the canal of Panama - without qualification. In all three polls, oppostiion to the treaties was expressed by about half the public (49-51 per cent), while just over a quarter (26-29 per cent) supported them.

A fourth poll at that time by Pat Caddell, the president's own pollster, said: "The government last week announced that we have concluded a treaty with Panama to return some parts of the canal, the Canal Zone, and operating revenues of the canal of Panama. From what you've heard, do you favor or oppose the treaty?" It is difficult to understand what Caddell meant by "some parts of the canal," but this made little difference to the public. It opposed the treaties by about the same margin, 46 per cent to 26 per cent.

But when the question of control begins to be qualified, the picture changes substantially. Consider the question Gallup has used: "The treaties would give Panama full control over the Panama Canal and the Canal Zone by the year 2000, but the United States would retain the right defend the canal against a third nation (emphasis added). Do you favor or oppose these treaties between the United States and Panama?"

It is this question, reflecting the greater complexity of the issue and put to those who were aware of the treaties, that produced the initial closer division and the January plurality supporting Senate approval.

There is more dramatic evidence of this point. Both NBC News in collaboration with the Associated Press, and CBS with The New York Times, took polls on the Panama treaties last October and this January. The initial questions, which made no mention of U.S. defense rights, showed similarly large margins opposed to the treaties.

But in the October CBS/Times survey, a second question was asked: "Suppose you felt the treaties provided that the United States could always send in troops to keep the canal open to ships of all nations. Would you approve of the treaties?" The result showed a complete reversal - from opposing the treaties by 49 per cent to 29 per cent, to favoring them by 63 per cent to 24 per cent.

In the January NBC News survey, this follow-up question was asked: "Would you favor or oppose approval of the Panama Canal treaty if an amendment were added specifically giving the U.S. the right to intervene if the canal is threatened by attack?" Again the results abruptly reversed. The original question showed 62 per cent to 28 per cent opposed to the treaties among those who had heard or read about them, but the second question produced a 65 per cent to 25 per cent margin in favor of such amended treaties.

With the U.S. right of military intervention provided, the results of the two polls are almost identical: a whopping 39-point margin of approval in the October CBS/Times poll, and an equally impressive 40-point margin of approval in the January NBC poll.

Still other evidence supports this point. A poll taken by the Field Institute in California asked the following question in October, 1977, and again in January, 1978: "As you may have heard, the Panama Canal treaties all for the gradual transfer of controls over the canal to the country of Panama by the year 2000 with the United States retaining military defense rights (emphasis added).From what you have seen or heard, do you personally approve or disapprove of these treaties?"

The results were similar to Gallup's nationally. Californians disapproved of the treaties by 49 to 35 per cent in October, a 14-point margin. In January, the results were much closer - 46 per cent disappoving and 41 per cent approving, a 5-point margin.

In short, Americans are by now about evenly split over a treaty that would provide for our right to defend and protect the canal, and they are very much in favor of a treaty that would allow for U.S. troop intervention in case of any threat to the canal. President Carter got to the crux of the matter in his Feb. 1 speech to nation when he stated that "the new treaties give us what we do need - not ownership of the canal, but the right to use it and protect it." Indeed, he indicated that he would not hesitate "to deploy whatever armed forces are necessary to defend the canal." Little Evidence of Militarism

IT IS POSSIBLE to read these results as an assertion of American militarism. Many commentators have suggested that what lies behind opposition to the treaties is frustration over the loss of Vietnam and the perceived decline of American power. Undoubtedly, many conservatives perceive the canal treaties as a symptom of American military retreat and feel that rejection of the treaties would demonstrate that the United States will not be pushed around by small countries.

Yet, curiously, there is little evidence of militarism or aggressiveness in the public's feeling about the canal.

In his October, 1977, survey, Gallup asked those who had heard or read about the canal debate: "What do you think are the best arguments against the treaties?" One answer stood out: "We built it and paid for it - we should keep it." This reason was given by a quarter of those asked. Not one response mentioned frequently enough to be counted could be classified as "militaristic" or "aggressive."

The second most popular argument against the treaties, "national security," was offered by only 10 per cent, and 5 per cent gave each of the following arguments: "I don't trust the Panamanian government," "The Panamanian government eventually won't let us use the canal," and "Communists will take it over."

Similarly, a January, 1977, survey by the Roper Poll offered those who opposed the treaties a list of arguments and asked them to choose the ones they found the most compelling. The two most frequently chosen (by about half the opponents) were that "We not only paid for the canal originally, but we have also paid a yearly fee to Panama for U.S. rights in the Canal Zone," and "When we made the Panama Canal treaty, it was supposed to last forever." About a third of the opponents chose the following arguments: "If we don't keep control of the canal, it could be invaded and taken away from Panama," and "If we don't keep control of the canal, the Panamanians might not let us use it."

Thus the most popular arguments against the canal treaties seem to be legalistic and defensive, not aggressive.

The legalism surrounding the debate has to do with ownership and sovereignty. The most compelling reason given by Americans for opposing the treaties is that the canal is our - "We built it and paid for it." In the same poll, Gallup asked respondents to identify the best arguments in favor of the treaties. The most frequently mentioned reason: that the canal "belongs to the Panamanians - it's part of their land." It's theirs The Deeper Feelings

IT IS LIKELY that claiming the canal is "ours" expresses more than a legal opinion or a recitation of what Americans learned in grade school. President Carter touched on this deeper attachment when he cited the view of David McCullough, a leading authority on the history of the Panama Canal, that the canal is "something that we built and have looked after these many years; it is 'ours' in that sense which is very different from just ownership. It expresses deep and elemental feelings about our own strength."

Dr. Robert M. Dorn, professor of psychiatry at the Eastern Virginia Medical School, describes this attachment in clinical terms:

"Any political talk that implies that we are giving away something which is currently viewed in fantasy as a part of ourselves, or possibly being 'robbed' of something which is a part of us, will certainly stir up a response. If such key words as 'ours,' 'giving away' and 'robbed' don't work, there is always the back-up idea of others wresting away control of this 'essential link' that keeps our 'country intact.' The fragmentation of our nation is, indeed, a frightening fantasy."

Americans' attachment to the canal can be described as primordial. We created it. We succeeded where the French had failed. We built it in a humanitarian way, by first wiping out the disease and suffering that had impeded other canal projects. We gave independence to the Panamanian people (though not without ulterior motives), and we created an unnatural resource which has brought great material benefit to Panama. Americans regard the Panama Canal as a monument to our technological know-how and to our humanitarian instincts, as a symbol of Yankee ingenuity, not Yankee imperialism.

Anti-treaty leaders have recognized that beneath the canal debate is this most fundamental of American values, the veneration of property rights. In an August, 1977, "Meet the Press" interview, for example, Republican Sen. Strom Thurmond of South Carolina declared that "I think the world is going to have more respect for us if we stand for property that belongs to us," and he concluded the interview by stating: "I think we cannot afford to let other people take our property, and I think we would have to take whatever reasonable steps are necessary to protect the property of the people of this country."

What puzzles many Americans about the treaties is that they do not see a clear reason for them. Why are we doing this? Who is pressuring us to renegotiate the status of "our" canal?

They refuse to accept arguments that the canal is "no longer important to us." In September and October, 1977, the Field Institute asked a sample of Californians how they felt about the statement: "The Panama Canal is no longer vital to U.S. defense." The sample disagreed, 62 per cent to 27 per cent, with close to half the sample, 43 per cent, disagreeing strongly. Even those who favored the treaties were evenly divided over this issue; 47 per cent agreed that "the Panama Canal is no longer vital to U.S. defense," and 47 per cent disagreed. As columnist George Will has written, "It is folly for advocates of the treaty to denigrate the canal's importance."

Given these strong feelings, it is not surprising that many Americans are nervous about sabotage, nationalization, or takeover by an unfriendly power. Americans feel secure about the canal only if it is under our own military protection. It is in this light that one should interpret the insistence upon the right of military intervention - not as aggression, but as defense.

All polls show that approval of the treaties increases markedly with education. The college-educated are often more favorable toward the treaties than are those under age 30 or self-described liberals.

This does not mean, as the Carter White House has suggested, that increased awareness of the treaties produces greater support for them. While those aware of the treaties have tended to be more supportive, this is largely because they have been better educated. Indeed, increasing awareness among those with similar education levels has done nothing more than build both opponents and supporters - it has simply increased the number of opinions. Education level has been the key.

The well-educated tend to have a broader world-view, to understand more complex and remote causes, to give more support to policies that involve no immediate, palpable benefits. Support for the treaties chiefly appears to come from well-educated internationalists who feel that the pacts will be seen as an act of fairness and generosity, that the ultimate payoff will be improved relations with the Third World and increased U.S. influence there.

In last October's Field poll in California, the following statement was the one which sharply divided supporters and opponents of the treaties: "Transfer of the canal to Panama would lead to improved U.S. relations with natiions in Latin America and elsewhere in the world." Californianas who supported the canal treaties overwhelmingly agreed with statement, 82 per cent to 11 per cent. Those opposed disagreed with the statement, 68 per cent to 28 per cent.

The fact that internationalists are more sophisticated does not necessarily mean they are right. The Vietnam war is a good example of a policy initiated by internationalists who saw sophisticated reasons why the United States would pursue a long-term, limited-war strategy. Non-internationalists asked "simple-minded" questions: "Why are we involved in this war if we don't intend to win it?"

In the canal debate, the non-internationalist public is asking many sensible questions about whether the United States is taking too great a risk in return for intangible gains.

Contrary to popular impressions, though, the implication of this position is that opponents of the treating have the more isolationist perspective. What they evidently are worried about is that turning control of the canal over to Panama would increase the likelihood of "trouble" and of the need to for U.S. military intervention. It is logical for isolationists to feel more secure with the canal under American control and protection.

The idea that the canal treaties represent an internationlist position helps explain another curious fact about them - that they are supported by virtually the entire political elite. No major Democrat has attacked the treaties, and most mainstream Republicans, including former President Gerald Ford and former Secretary of State Henry Kissinger, have endorsed them.

Indeed, responsible politicians like Senate Minority Leader Howard Baker of Tennessee have had to got out of their way to find sensible reasons for opposing the canal treaties. Baker is under considerable pressure to conform to the official Republican opposition to the treaties, especially if he expects to be a contender for the 1980 GOP nomination. But he also shares the pro-treaty bias that characterizes the entire "internationalist" Washington community. The Intensity Factor

IT MAY BE that the President's Feb. 1 speech has helped turn public opinion around on the treaties, but that still may not assure two-thirds approval by the Senate.

This is because of another aspect of public opinion: intensity. Several polls have shown that opponents feel more strongly about the pacts than supporters. In the October, 1977, CBS News/New York Times survey, respondents were asked, "Do you feel strongly enough about the way your senators vote on the Panama Canal treaty to change your vote because of it when they run again?" Among treaty supporters, a 56 per cent majority said "no," while only 26 per cent said that they would change their votes because of the treaty issue. Among treaty opponents, however, the balance was reversed: a 44 per cent plurality said they would change their votes depending on how their senators voted on the treaties, while 34 per cent said the treaty would not be their sole consideration.

These crude indicators of intensity suggest what many politicians already realize: that treaty opponents are beginning to look like a veto group. They are already communicating their intent to defeat any senator who votes to approve the treaties. Thus even if public opinion shifts decisively in favor of the treaties, senators may still not fall into line. A senator will realize that he stands to lose many more votes from the anti-treaty minority than he has to gain from the pro-treaty majority.

An organized veto-group - those opposing abortion, gun control, and the ERA, or the anti-war movement during the Vietnam years and the pro-Israel constituency - can operate effectively with or without the support of public opinion. Such groups are particularly potent in the treaty-approval process, where only one-third of the Senate can block a pact. Every wavering senator will be forced to balance several cross-cutting influences: public opinion, the likelihood of an organized campaign against them if they vote for the treaties, pressure from the White House, pressure from their party, from the Washington milieu, from their own private convictions. It is the uncertainty of the process that makes it interesting - and democratic.