ONE FRINGE BENEFIT of poring over all those briefing materials from the 1980 presidential debate is the chance to reflect on how different Ronald Reagan's carefully scripted remarks sound a scant 32 months later.

To be sure, misleading campaign promises have been something of an American tradition, at least since President Johnson told us in 1964 that he would not send American boys to fight an Asian war. No one appreciated this more than Reagan, whose briefing book for the debate with President Carter produced a neat list of 227 broken promises from Carter's 1976 campaign.

But replaying the Cleveland debate in 1983 shows not only that Reagan's rhetoric has exceeded his grasp, but that in a number of instances he has taken the country in an almost diametrically opposite direction.

On the economy, for example, Reagan declared: "President Carter . . . can't hide the fact that there are 8 million men and women out of work in America today." That seems modest by today's measure, with 11 million jobless and a double-digit unemployment rate showing no signs of descending to the 7.5 percent level of October 1980.

Reagan went on to add, almost exactly as it was written in the briefing book: "If all of the unemployed today were in a single line, allowing two feet for each of them, that line would reach from New York to Los Angeles, California." By now, the line might stretch to El Salvador.

Reagan's briefing book told him that he could score points by proclaiming that Carter's "four-year deficit is biggest of any president in history. . . . Highest interest rates since the Civil War. . . . Carter also fails to appreciate the suffering."

The candidate took his cue in the debate, making a pitch for his supply-side tax cuts, and adding: "I have submitted an economic plan that . . . can provide for a balanced budget by 1983 if not earlier."

Well, we all know how that one turned out: record interest rates and a string of $200 billion federal deficits as far as the eye can see.

Reagan should be given credit, naturally, for bringing down inflation. But in the wake of the deepest recession in a generation, it's hard to forget one of Reagan's more indignant debate comments: "Mr. Carter had also promised that he would not use unemployment as a tool to fight against inflation."

The Reagan team knew from reading Carter's briefing materials that Carter would accuse him of planning to slash vital domestic programs. Reagan tackled the issue head on.

"Well," he began, "most people, when they think about cutting government spending, they think in terms of eliminating necessary programs or wiping out something, some service that government is supposed to perform. I believe that there is enough extravagance and fat in government . . . that there is probably tens of billions of dollars that is lost in fraud alone. . . . I'm confident that it can be done. . . ."

After $40 billion in first-year domestic cuts, after slicing into food stamps and Medicaid and housing and school lunches, that celebrated fat is a bit harder to find.

Reagan also repeated his promise to abolish Carter's newest agencies. "The Department of Energy has a multibillion-dollar budget in excess of $10 billion. It hasn't produced a quart of oil or a lump of coal," he said. We haven't heard much lately about his pledge to abolish this agency or, now that the schools are back on the front page, the Education Department.

Perhaps the most important issue in the 1980 campaign was Carter's charge that Reagan would lead the nation into a dangerous arms race. Reagan flatly denied: ". . . I would say to the Soviet Union, we will sit and negotiate with you as long as it takes, to have not only legitimate arms limitation, but to have a reduction of these nuclear weapons to the point that neither of us represents a threat to the other."

The Soviets apparently haven't gotten the message. After 21/2 years, not only do the arms control talks remain stalled in Geneva, but Reagan recently had to reassure members of his own party, when they balked at approving the MX missile, that he would get serious about reaching a strategic arms agreement.

There was a host of other briefing book lines that Reagan didn't get a chance to use on television. On environmental protection, for example, the book said, "RR bows to no one in commitment . . . move positively on urgent environmental problems . . . must be no more Love Canals." Maybe he forgot to tell that to Rita Lavelle and her crew at the EPA.

And Reagan was prepared for the charge that his tax cuts would favor the rich. Had Carter dared to press the issue, Reagan would have said: "When Mr. Carter came back from Texas last week, he brought some of that horse manure with him. He's absolutely wrong about these tax cuts -- everyone in America gets the same cut in tax rates over the next three years."

Why is it, then, that we keep reading about how the tax cuts have been a particular boon for upper-income families?

In the end, the voters refused to swallow the Carter line, but some of his criticisms have since ripened with age. The Reagan briefing book devoted a chapter to reciting "Carter Attack Lines," using some of the same wording as Carter's own briefing documents, and it carries a strange echo:

"RR can't cut taxes, raise defense spending and balance the budget -- unless he uses mirrors or drastically cuts social programs. . . .

"RR plan is Robin Hood in reverse -- take from the poor and give to the rich. More GOP trickle-down. . . .

"RR has been insensitive to the needs of blacks and other minorities. Would divide nation. . . .

Of course, Carter engaged in substantial hyperbole about his own record, and undoubtedly would be vulnerableeto the same kind of retrospective analysis if he had been reelected. All it takes is a look back at what Jimmy Carter said in one of his 1976 debates with President Ford:

"I believe by the end of the first four years of the next term we could have the unemployment rate down to 3 percent . . . a controlled inflation rate and . . . a balanced budget."

Well, there they go again.