White House and congressional budget negotiators have had more than the portraits of George Washington and former Senate majority leader Mike Mansfield (D-Mont.) gazing down on them as they met in a dark-paneled, windowless room off the Senate chamber during the last month.

They have been haunted by the ghosts of budget battles past.

For Democrats, it is the specter of Walter F. Mondale carrying their party's banner to its greatest electoral defeat in more than a century after pledging to raise taxes to reduce the federal budget deficit.

For Republicans, it is the vision of the 26 House seats the GOP lost in 1982 after then-Speaker Thomas P. "Tip" O'Neill Jr. (D-Mass.) assailed them as enemies of Social Security and the elderly.

These politically gruesome apparitions are among the strongest forces shaping the budget talks, according to congressional bargainers. They threaten to frighten the negotiators away from such sensitive issues as taxes and Social Security benefits that many say are key to a meaningful deficit-reduction package. They complicate even moving the discussions along.

"Each party has used these issues to beat the hell out of the other," said Rep. Leon E. Panetta (D-Calif.), chairman of the House Budget Committee. "My problem is that they've done it successfully."

"When you ask them to come together and do things that could expose each party to its worst nightmare of political attack, it's not easy to do," House Speaker Thomas S. Foley (D-Wash.) said. "This is a tough hill to climb."

The next two weeks will be crucial for the budget talks, negotiators said, indicating whether the bargainers will make it to the top of the hill or, like the doomed Sisyphus of Greek mythology, go sliding back down the slope.

House Majority Leader Richard A. Gephardt (D-Mo.), who presides over the talks, has vowed to work into the night and over weekends in hopes of reaching at least the outlines of an agreement before Congress goes home for the July 4th holiday recess. "We need to get this thing moving," said a Bush administration official.

A more realistic goal, others have said, is to know by then whether such an agreement is possible.

Congressional bargainers said they hope this week will mark the end of what has resembled a symposium studying the problem -- a process Sen. Wyche Fowler Jr. (D-Ga.) likened to "dancing through the minefields" -- and the start of serious bargaining aimed at solving it.

But the same memories of past political warfare that make ultimate agreement difficult hinder moving the talks into the new phase.

Neither side wants to be the first to propose politically unpopular solutions. "Everybody is waiting for the other one to make the first move so they can laugh it off," said Rep. Bill Frenzel (Minn.), the House Budget Committee's ranking Republican.

In the two most recent previous rounds of budget talks, participants assembled proposals, often on a bipartisan basis, from menus of options prepared during the preliminary stage.

But participants said that is not likely to work this time. "You've got too many people waiting for the magic words," said Panetta, a veteran of the 1987 and 1989 budget talks.

One of those words -- "taxes" -- is so sensitive that nervous laughter greeted White House Office of Management and Budget Director Richard G. Darman when he stumbled on the word "revenue" at one point during last week's sessions, according to participants. "I can't even say it," bargainers recalled Darman joking.

Democrats remain adamant that President Bush make the first move. "We have to start all over" with a presidential budget request, said Senate Budget Committee Chairman Jim Sasser (D-Tenn.). "They say their budget is now obsolete and they say our budget resolutions are obsolete."

Darman has not indicated how he intends to proceed. Administration officials have suggested that one way to get things started would be to raise previously proposed deficit-reduction packages. The most prominent of these came from House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.), who called in March for an ambitious five-year $511.6 billion mix of tax increases and spending cuts.

But Rostenkowski has warned Darman not to raise the plan unless the Bush administration is ready to endorse it, according to bargainers.

And even if those around the negotiating table reach an accord, the politics of deficit reduction will present obstacles to congressional approval. Lawmakers' intrinsic aversion to raising taxes and cutting benefits is complicated this election year by campaign stands. Candidates for reelection are locking their positions on the issues, which will limit their flexibility should a deficit-cutting agreement come to a vote.

"We have members who are pre-positioning themselves," Foley said. "People are creating situations where they couldn't possibly bring together an agreement out of their statements."

The success of the upcoming negotiations will depend in large part on the groundwork that has been laid in the eight days of meetings that have taken place.

The sessions have been part seminar, part encounter group, educating lawmakers and administration officials on the vagaries of the $1.2 trillion federal budget and trying to build trust among the sometimes suspicious bargainers.

"We've been feeling each other out, figuring out whether there are traps being set or not," said Panetta. "The real test of whether it has been worthwhile will be that first day of real negotiation."

"I don't know where we are on trust," said Frenzel. "We all have some, maybe we don't have quite enough."

Gephardt said the work has "not been unproductive." Others seem to have found it less helpful. White House Chief of Staff John H. Sununu, for instance, spent most of the sessions reading newspapers and unrelated paperwork, according to participants.

The sessions, participants said, have had moments of levity, but even the humor carries a bite.

Early on, for example, Darman challenged Panetta's claim that the House-passed budget would pare $36 billion off next year's deficit, laughingly calling some of its provisions "Stockmanesque" -- a reference to David A. Stockman, President Ronald Reagan's first OMB director renowned for his proficiency in manipulating the budget process.

Not all of the barbs have been between members of opposite parties, either, according to participants.

During a discussion of foreign aid last week, Rep. Mickey Edwards (R-Okla.) of the House Appropriations subcommittee on foreign operations likened defaulted foreign loans to the savings and loan crisis.

Treasury Secretary Nicholas F. Brady took issue, saying that thrifts were ruined by "fools who ran off with the money."

"How about the fools who gave it to them?" interjected Sen. Phil Gramm (R-Tex.).

Brady paused briefly, looking askance at Gramm, before continuing, participants said.

Staff writers Dan Balz and David S. Broder contributed to this report.