From Marion G. (Pat) Robertson and Paul Laxalt on the Republican right to Jesse L. Jackson and Rep. Patricia Schroeder (D-Colo.) on the Democratic left, 1988 presidential contenders are telling audiences around the country that the time has come to end the Reagan military buildup.

This emerging line of thought is a sharp reversal from the previous two presidential elections, when nearly all candidates in both major parties shared the general proposition that defense spending should be steadily increased to keep the nation secure against foreign threats.

Today, the opposite position -- that the Pentagon's budget must be frozen or cut -- has become the mainstream view among Democratic candidates, and it is gaining support among Republicans as well.

A majority in Congress has already made it clear that the large Reagan buildup will be stopped, at least in the upcoming fiscal 1988 budget. Rejecting the administration's request for another defense spending increase, Congress seems likely to approve at most a budget that would hold the Pentagon at its current spending level with an adjustment for inflation.

The new view of defense spending in Congress and on the campaign trail stems from concern over the federal budget deficit, which most presidential candidates are calling the chief governmental problem facing the nation. It is also driven by a general sense among the candidates that the Pentagon has been wasteful in using the large budget increases received under Reagan.

But to a great degree, the politicians' shift on defense reflects a similar shift among the American people, a national change of mind that has been brought home clearly to the candidates -- and their pollsters -- over the past year or so. In an era of $200 billion deficits, the polls say, the national consensus for increasing defense spending has evaporated.

"Any way you ask it, in almost any region of the country, it's clear that people have changed on this. They're ready for a cut in defense spending to balance the budget," says Paul Maslin, a Washington-based polling expert who works with Democrats. "When you ask how to go about reducing the deficit, {cutting} defense is clearly the first choice."

A Washington Post-ABC News poll in June demonstrated the point. Among those surveyed, 70 percent said it would be better to cut the defense budget than to let the deficit grow any higher.

Then the respondents were asked to set priorities for cutting the deficit. Given the choice between reducing defense spending or cutting social programs, 65 percent of those surveyed opted for defense cuts. Asked to choose between lower defense spending or higher taxes, 66 percent preferred the defense cut.

Within the administration, President Reagan and Defense Secretary Caspar W. Weinberger say it would be a mistake to end the pattern of regular annual increases in defense spending that has prevailed for the past decade. They contend that the Pentagon budget must be increased at an annual rate greater than the rate of inflation for at least five more years to assure security.

But this position has been rejected in Congress; the budget for fiscal year 1988 will probably include little or no increase in defense outlays over the current figure of $289 billion. And now several presidential candidates are directly challenging a continuation of the defense buildup, one of Reagan's most cherished policy initiatives.

In the 1988 election, evidently, cutting defense spending will not be strictly a liberal position. As evidence, consider the stance of Republican presidential hopeful Robertson, the prominent television evangelist who is generally considered a strong conservative. Robertson is telling voters that the deficit is such a crucial national problem that every area of federal spending, with the exception of interest on the federal debt, should be cut to help balance the budget.

Asked in an interview last week whether this would include a cut in defense spending, Robertson replied, "Oh, absolutely. Absolutely. I think we can get the same defense with less money."

Robertson would not specify which defense projects he would cut. "They say it's suicide at this stage of things to get too precise," he explained. Nor would he say how much he would cut below current levels. He spoke of savings in the range of $30 billion or $40 billion, although he said he was not sure how much total reduction is possible.

Another Republican candidate, former Nevada senator Laxalt, takes a similar position. To help balance the budget, Laxalt said through a campaign spokesman, every department of government should be cut, including the Pentagon. He said any program, military or domestic, could survive a budget cut of 10 percent or so without serious impairment.

Sen. Robert J. Dole (R-Kan.) has voted for the Reagan arms buildup in the past, but this year he did not support the administration request for a spending increase about 3 percent above the projected rate of inflation. Dole voted for a defense increase at the rate of inflation, which amounts to a spending freeze in real dollars. On the stump, Dole has told voters that defense spending might have to be frozen or cut to help deal with the deficit, vowing not to exempt the Pentagon from an overall budget cut.

The other Republican candidates all support continued increases in defense spending beyond the rate of inflation.

Jackson, in some ways the most liberal of the Democratic candidates, was virtually a voice in the wilderness in the 1984 presidential campaign when he called for a 20 percent cut in Pentagon spending. This year Jackson still advocates a defense spending cut, although he no longer specifies 20 percent. But now Jackson finds himself just a voice in the crowd of Democratic candidates who say it is past time to stop increasing the defense budget.

Sen. Joseph R. Biden Jr. (D-Del.) says he plans a cut of about $10 billion from the fiscal year 1988 defense budget, which is likely to total just under $300 billion. Former Arizona governor Bruce Babbitt (D), Massachusetts governor Michael Dukakis (D), and Colorado Democrat Schroeder all say they would push for a cut in overall defense spending if elected.

Rep. Richard A. Gephardt (D-Mo.) and Sen. Paul Simon (D-Ill.) have voted in Congress this year to freeze defense spending at the current level. Both say that they would freeze or cut the defense budget if elected.

Sen. Albert Gore Jr. (D-Tenn.) declined to say whether he would cut defense spending if elected. Taking a position similar to that of Gary Hart in the 1984 campaign, Gore said, "The proper questions are not how much or how little, but how well it will be spent and for what."

If the next president does bring about a defense spending cut, it would mark a reversal of one of the most striking developments of the Reagan presidency. When he took office, Reagan inherited a budget from Jimmy Carter that called for $136 billion in defense outlays, according to Office of Management and Budget figures. The current defense budget of $289 billion represents an increase of more than 100 percent over seven years, during a period when inflation has been relatively low. Reagan administration projections call for additional increases over the next five years to an annual budget of $386 billion by fiscal year 1992.