The moment when the budget summiteers ran out of political oxygen and retreated to safer altitudes came last Monday morning in a small corner office on the third floor of the Capitol.

As a crowd of impatient reporters settled into chairs in the House Rules Committee room, an aide pushed a dolly with a television monitor and video recorder into place at the center of the dais -- the spot usually occupied by the panel's chairman, Rep. Claude Pepper (D-Fla.).

The aide slid a cassette into the machine and fumbled momentarily with the controls. Onto the screen came Pepper -- a hero to the nation's elderly -- with a short videotaped message from Florida that extinguished whatever flickering hope remained for a bold deficit-reduction compromise that would include reductions in Social Security cost-of-living adjustments (COLAs) and other inflation allowances for federal workers and retirees.

Pepper's unstated threat that day, reinforced by the presence of officials from organizations representing tens of millions of teachers, federal employes and retirees, was that any tinkering with Social Security or other COLAs would bring reprisals at the polls next year.

Twenty-four hours earlier, several key congressional leaders who had spent the past three weeks in budget talks with top Reagan administration officials had appeared on Sunday television talk shows, where they also poured cold water on the prospects of Congress approving any agreement that dug into COLAs.

Across the Capitol, where the budget negotiators were closeted in the Lyndon B. Johnson room that Monday morning, the effect of the two events was immediate and apparently irrevocable. Gone from the wall was the full-page newspaper ad that was hung the previous Friday urging the nation to support a "bipartisan budget plan" and appealing for "bold political action."

The disappearance of the newspaper ad was symbolic of the mood that dominated the talks as they limped toward Friday's agreement between President Reagan and Congress on a $30.2 billion plan to reduce the deficit this year. From that point on, negotiators ignored the ad's admonishment that they "rise above politics as usual."

To many lawmakers on Capitol Hill, including some who participated in the protracted negotiations spurred by the Oct. 19 stock market plunge, the accord reached Friday represents a disappointing reversion to political form by everyone.

"The problem is the political scars of eight years of political battles between the parties are still showing," said Rep. Leon E. Panetta (D-Calif.), a regular participant in the talks who fought to include COLAs in the mix of deficit reduction. "The scars of those battles are seen in this package."

House Speaker Jim Wright (D-Tex.), expressing disappointment that the package was not more "heroic," said the talks fell short because "we didn't have enough heroes."

The limited scope of the budget agreement, which without a one-time, $5 billion sale of federal assets would barely exceed the $23 billion automatic spending reductions required by the budget law, is one reason that implementing the plan through separate legislation in December may be difficult.

Even as congressional leaders were driving to the White House on Friday to announce their agreement with Reagan, Republicans and Democrats were taking to the Senate floor to promote an alternative. Pushed by a bipartisan group led by Sen. Nancy Landon Kassebaum (R-Kan.), the plan would freeze all federal spending, including COLAs, at this year's levels. Combined with a delay in lowering tax rates, that plan would save about $30 billion.

But revisiting the politically delicate issue of COLAs is probably out of the question even though delaying or cutting the allowances for federal workers and retirees could add billions of dollars in deficit reduction to the package. When the talks began, Reagan took Social Security off the table, and despite repeated discussions of it by some negotiators, it stayed off.

The president's early remarks, Panetta said, "created a political situation where someone had to put it on, and made it difficult for one party or the other to assume the responsibility. We had to have political leaders on both sides take the position, and that chemistry never came together."

That left negotiators essentially nibbling at the margins of the budget and re-fighting political battles that had grown all too familiar during the Reagan years. The talks became a kind of trench warfare in which ground that had been fought over for years was revisited again and again in ever smaller pieces.

"We'd be doing exactly what we are doing today if the Dow was at 3,000 and everybody was celebrating on Wall Street," said House Majority Leader Thomas S. Foley (D-Wash.) on Nov. 13. "There are people in this group who have clearly different priorities on the federal budget. The administration wants higher defense than any Congress would give them. The administration wants to reduce domestic discretionary spending to a level that is not agreeable to both parties in Congress. And the administration has had an allergy to general revenues."

An illustration of the dynamics came on a day when negotiators haggled over a $500 million difference in defense spending, which this year is likely to total about $285 billion.

The argument left House Minority Leader Robert H. Michel (R-Ill.) sputtering in frustration. "It's like the whole damn fleet is going to sink and the whole Air Force is going to drop out of the sky because they can't get that last half-billion dollars," Michel said.

Complicating the process was the fact that the negotiations weren't just between two parties, the Reagan administration and Congress. They were among the administration and the rich variety of factions, which have widely differing agendas, that make up the two houses.

Senate Republicans, for example, were more willing to bite the cost-of-living adjustment bullet than their House colleagues. Senate Democrats, however, were less inclined to cut defense than many of their compatriots in the House.

And overshadowing the whole exercise was the 1988 elections, which produced pressures that will continue to buffet the House and Senate as they draft and vote on measures to write the accord into law.

Some House Republicans who have followed their president's lead in opposing tax increases now feel betrayed by Reagan's reluctant acquiescence, which has undercut a significant campaign issue for them. Some liberal Democrats feel they were sold out on the issue of defense spending and would prefer higher taxes aimed at the wealthy.

Presidential politics was also a factor, said some Democrats, who attributed acerbic criticism of the package from Senate Minority Leader Robert J. Dole (R-Kan.) to advertisements run in New Hampshire by a rival for the GOP presidential nomination, Rep. Jack Kemp (R-N.Y.), questioning Dole's tax-cutting credentials.

Nowhere were the political pressures more evident than on the cost-of-living adjustment issue. Democrats said that the senatorial ambitions of a key GOP negotiator, House Republican Whip Trent Lott (Miss.), stiffened his resistance to tinkering with COLAs. Sen. Lawton Chiles (D-Fla.), who faces a 1988 reelection campaign in a state heavily populated by the elderly, also was said to have raised objections to reducing COLAs, though less vigorously than Lott.

The issue was particularly sensitive for Republicans, who feel they have been burned on it before: in 1982, when they lost 27 House seats, and in 1986, when they lost control of the Senate following a 1985 vote, spearheaded by Dole and later undercut by Reagan in an alliance with House Democrats, to freeze cost-of-living adjustments.

Democrats, said Rep. Steny H. Hoyer (D-Md.), whose district includes large numbers of federal employes, were willing to reduce COLAs. "However, that was premised on the fact it couldn't be done alone, that we needed substantial Republican and presidential support. If Lott was yelling, a lot of Democrats were saying, 'I'm not going to get off the dime.' "

But administration officials said the Democrats were demanding too much in return for pushing COLA reductions: several billion more dollars in taxes, aimed at the rich.

"It was clear toward the end of the discussion that the Democrats were going to exact a very high price," a senior administration official said. "They kept saying, 'Oh yeah, we ought to do something about the COLAs.' And then they turned around and said, 'If we're going to give up our COLA issue, we've got to get something in return. The administration has to agree to forgo lower marginal tax rates {in the 1986 tax law}, or it has to agree to soak-the-rich tax items.' Now, the president is just not going to accept something like that. So I think it was clear that the asking price was just too high."

The cost-of-living adjustment issue was settled in a meeting of three senior administration officials and five congressional leaders, according to one of the participants, who said they determined that cutting the COLAs as part of the package was unworkable. "I think by the beginning of {last} week it was understood by almost everyone that COLAs were not going to be part of the package," the negotiator said.

The result of those political cross-currents is a package that is considerably reduced in scope, that reflects the longstanding political and fiscal standoff between the administration and the Democratic-controlled Congress, and that is cobbled together with some spending savings that many find highly dubious.

As congressional committees must decide in the next two to three weeks which taxes to raise and which programs to cut, the package's prospects appear uncertain.

Reagan and congressional leaders began the job of selling it yesterday. In his weekly radio address, the president called the agreement "probably not the best deal that could have been struck" but urged its passage as a good starting point.

In the Democratic response, Chiles said the plan offers "real" savings with "no gimmicks, no accounting tricks, no smoke, no mirrors."

Supporters of the bargain between Reagan and Congress argue that critics will come around rather than let $23 billion in automatic spending cuts take place as required by the Gramm-Rudman-Hollings deficit-reduction law.

But when Congress left for a week-long Thanksgiving recess, resistance still appeared formidable.

Republicans, Rep. William S. Broomfield (R-Mich.) said on Thursday, "are still insisting on no new taxes, and they're being very hard-nosed about it."Staff writer Paul Blustein contributed to this report.