THIS MAY GO down in political annals as the Year of the Invented Mandate.

Treasury secretary Donald Regan, defending the administration's three-year tax cut plan, proclaims that the president "was elected on this basis." Vice President George Bush declares that congressional opponents of the president's spending and tax cut proposals would "in effect thwart the mandate of the people."

Budget chief David Stockman adds his assertions that cuts in social programs are dictated by the elections, and Nevada Sen. Paul Laxalt defends anti-abortion, pro-capital punishment and other conservative social causes by contending: "that's what the election was all about. It is part of the Reagan mandate."

All this may or may not be good politics but it certainly is nonsense, and awfully repetitious nonsense at that. If administration officials are going to keep it up, there is little choice but to repeat back, emphatically: That is not what the election was about. The accumulating evidence makes it quite clear that the November returns provided none of these claimed mandates, just as they did not represent the broader "historic political realignment" that more than a few observers have suggested.

The more limited and tentative messages of the election are particularly evident in the emerging findings of our 1980 American National Election Study at the University of Michigan's Institute for Social Research (ISR). These, I think, bear some scrutiny if we are to avoid, on this and other scores, the kind of inflated rhetoric which is not merely contrary to the majority's wishes but which may ultimately lead us back to deep disillusionment with our political system.

Consider, for example, Secretary Regan's imagined tax mandate. The reality, our study shows, is that less than half the Republicans and independents and only a third of the Democrats who voted for President Reagan favored his three-year tax cut proposal. The president clearly was not "elected on the basis," and later evidence gives no reason to believe his tax plan has inspired more confidence since November.

A nationwide poll taken in mid-April by the Los Angeles Times found that less than half of all registered voters interviewed thought a Reagan-style, across-the-board tax cut would get the economy moving again. Similarly, the separate May ISR Survey of Consumer Attitudes showed that only 41 percent of respondents thought they would be better off if President Reagan's plan to reduce federal taxes and spending were enacted.

The same holds for the administration's across-the-board cuts in social programs. The election provided no "mandate" for this drive, no matter what David Stockman pretends. On the contrary, our study confirms other findings showing that voters in 1980 continued to express their long-standing support for these programs. In the education area, voters in November even expressed a slightly increased preference for government spending, not the cuts the administration is now pushing through Congress.

Indeed, reductions in government outlays per se were not as important as some have argued in determining the election outcome. Substantially less than half the Democrats who defected to Reagan, for example, expressed a desire for lower government spending.

Nor has any significant shift in preferences for social programs been detectable since the election. In April the CBS/New York Times Poll even reported that those identifying themselves as conservatives opposed spending reductions for such programs as the Comprehensive Employment and Training Act (government jobs for the unemployed) or loans to college students, both currently on the Reagan chopping block.

One could scarcely find better evidence of popular opposition to domestic spending reductions, in fact, than the fears of Reagan supporters about voting on individual program cuts in the House budget battle last week.

Least of all can one find evidence of Sen. Laxalt's mythical "mandate" on a social issue like abortion. If it needs saying again, in November, as for a decade, the country was firmly committed to a woman's right to have an abortion.

What did the electin say? It may leave political theologians on all sides unsatisfied, but the 1980 vote essentially was an expression of growing American worry about inflation and our slipping economic growth, as well as about U.S. military strength and prestige abroad -- not a clear endorsement of specific means for solving these universally recognized concerns.

In other words, despite the striking Reagan sweep of the electoral college, the 1980 election was not ideological in terms of issues. Our study shows that ideology in fact played a less important role in 1980 than it did in 1976 or 1972.

A majority of both Carter and Reagan voters, for example, favored increased military spending. But they did not view this suddenly acquired preference -- a response to events in Iran and Afghanistan -- as a tradeoff for reduced outlays in long-supported domestic social programs. Rather, our study makes clear, military increases were supported in addition to domestic programs.

Reagan administration officials understandably argue today that there is no way to attain an affordable compromise between "guns" and "butter," but voters in November accepted something else that candidate Reagan told them: that there is extensive waste and incompetence in government. The support for reduced spending that voters did express in the 1980 election, our study shows, was more a response to the belief that waste and incompetence can be cut in all areas, defense as well as domestic, than an ideological rejection of all Great Society programs.

The Reagan emphasis on defense spending also indicates a conviction that the most effective way to deal with sagging prestige abroad is through an increased military capability. But our study shows that much of the concern voters expressed in this area was based on what they saw as an inconsistent Carter foreign policy and an overly conciliatory relationship with the Soviet Union. In other words, the study suggests a voter belief that creative and consistent diplomacy and international leadership would do more to restore our international prestige than would a stronger military presence.

Nor did ideology have as much influence on the election as did public dissatisfaction with President Carter's handling of inflation and Iran. In November, the study shows, voters had little regard for either Carter or Reagan, but their dissatisfaction was directed more intensely at Carter and overshadowed ideological distinctions.

It should be abundantly clear from all this that Reagan did not have a mandate for most of his policies at election time and has not yet succeeded in establishing a popular consensus. The administration's repeated claims to "mandates" can thus be seen as part of its attempt to in fact create such a consensus today, either by inventing popular wishes or using selective evidence to support its case.

Hence, the administration can cite survey results showing a majority favoring increased defense spending but ignore the majority supporting more outlays for social programs. It can invoke the majority calling for decreased federal powers but conveniently forget the majority that wants a federal gun control law.

Whether this and other strategies succeed in building a popular conservative mandate and an enduring political realignment clearly depends on an array of factors -- Reagan's personal popularity (up significantly since the election), his job-performance rating (down lately), his ability to persuade, the corresponding ability of Democrats to emerge from disarray and articulate and persuade with popular candidates, to name just some.

Obviously, the chief factor will be whether Reagan succeeds in restoring health to the economy and American prestige abroad. If he does, he will no doubt be in a stronger position to promote other conservative changes and cement emerging Republican gains.

There has, of course, been an increase in persons identifying themselves as conservatives (from 37 percent in 1978 to 44 percent at the end of last year), even if such self-labeling does not indicate a concomitant shift to the right equally across policy areas.

Moreover, the South and the Mountain States have been experiencing what might be called a sectional partisan realignment. With the migration of more clerical and professional people to these regions have come both a larger Republican base and an increased population, giving Republicans greater clout in national elections.

In fact, this population shift, our study shows, played a more significant role than ideology in helping Republicans win control of the Senate, as did the precarious nature of Senate seats. (Contrary to popular preceptions, our studies have long shown that Senate seats generally have become less "safe" than House seats.)

Other groups in the past decade have also shown a steady shift from the Democrats and at least a potential for increased Republican identification. This has been particularly evident among Catholics and, to a lesser extent, among young people. While more than a third of adults today think of themselves as independents, they come disproportionately from younger age groups.

A serious political realignment, however, would still face major obstacles. Relatively few people switch party allegiances; it is rather those lacking party attachments -- predominantly those younger persons -- who present the chief opportunity for realignment, and these people do not have homogeneous political views. Although young independents look like Republicans in their views on certain economic programs, their preferences on social issues lie much closer to those of the Democratrs.

In additions, even if Reagan's policies were to improve the economic prospects of the young, the gain might not be dramatic enough to initiate a long-term partisan commitment or might not be seen as partisan at all. If any Reagan successes were seen as personal achievements rather than the result of partisan efforts, Republicans on the whole would not be likely to reap lasting benefits.

If the Reagan administration, on the other hand, fails to fulfill the large expectations which our studies show it has created -- renewed prosperity, reduced inflation, lower joblessness, a more equitable tax burden and greater prestige abroad -- certain results are fairly predictable.

Volatility in American politics would continue and Reagan would risk joining, involuntarily the growing list of one-term presidents. Traditional party loyalties -- Democratic as well as Republican -- would suffer a further decline, accompanied by increased challenges from monority parties and independent candidates. Cries for more extreme remedies to our problems would likely grow louder, and citizens fervor for changes in the candidate selection system and the political decision-making process might intensify.

At the same time, citizen frustration with government failures and the feeling that voting doesn't make a difference would continue to grow. Trust in government, which our study shows sank to a historic low just before the November election, would also decay again, more than offsetting the short-term gains evident with the election of a new president.

Perhaps most important, there might be a qualitative shift toward what appears to be a new ideology of discontent, one directed not at reform but dismantling government and its programs, regardless of future consequences. This ideology, based on an active rejection of political institutions and of authority, could take years to reverse.