In the final stages of his presidency, Ronald Reagan is turning to the right and hanging tough.

White House aides said Reagan's choice of Robert H. Bork to fill an unexpected Supreme Court vacancy and the resurrection of his old-time conservative economic agenda in a speech at the Jefferson Memorial on Friday both were parts of an effort to prevent his presidency from fading into the past tense under pressure from a restive Democratic Congress and the Iran-contra scandal.

Reagan has told White House chief of staff Howard H. Baker Jr., who made his reputation as a compromiser, that he wants no compromise on taxes. Last week, the president brushed aside assessments that Bork might face difficulty winning confirmation and said he wanted the U.S. appeals court judge anyway.

"It's very Ronald Reagan-like," Baker said of the Bork nomination on ABC News' "This Week With David Brinkley" yesterday. "He not only states his beliefs, he acts on them."

Baker added, responding to another question, that Reagan very much wanted an arms control deal with the Soviet Union, but said he would "walk away from it" if the terms were not favorable. "He's no patsy in the final 18 months of his term," Baker said.

On Friday, unveiling what he called an "Economic Bill of Rights," Reagan hardened a balanced-budget amendment that seemed to be going nowhere by adding a provision that made passage even less likely. The new proposal would require a "super majority" for Congress to raise taxes.

Reagan, who blames Congress for the record federal budget deficits of his seven years in the White House, was described by one official as "stirred up" by the opportunity to once more engage the Democrats on fiscal issues and by his unexpected new chance to possibly shift the balance of the Supreme Court.

At a Cabinet meeting on Thursday at which he outlined his "Economic Bill of Rights," the president remarked that he had watched a few minutes of the debate among the Democratic presidential candidates in Houston the night before. "Did you notice that their wave of the future is more government and less defense and that it takes us back 40 years?" Reagan said, according to an official who attended the meeting.

Some Republicans say that Reagan's renewed enthusiasm over his conservative agenda gives him a chance to regain the political initiative he lost late last year, when Democrats won control of the Senate and the Iran-contra scandal broke.

"I think he relishes the prospect of 18 months of campaigning for his issues and setting the agenda for the 1988 campaign," a senior White House official said last week. "It's had a regenerative effect on his work."

But other Republicans are worried that Reagan's turn to confrontation may have doomed the prospects of a genuine budget compromise with the Democrats despite Baker's determination to attain one. According to a senior administration official, Baker was headed toward a negotiated compromise with Democratic congressional leaders when he was personally deterred by Reagan, who made it clear he would not agree to revenue increases of any sort.

"This president doesn't want to be told that he can't sustain the highway bill veto or that he will find it difficult to get Bork confirmed," said one White House official. "He wants you to find a way to do what he wants to do."

A longtime Republican associate said there was "genuine tension" between the immediate goal of "keeping Reagan interested in his presidency" and the long-term one of leaving "a useful legacy" of an arms control agreement with the Soviet Union and a budget compromise. This associate said that Reagan wanted the arms control agreement but was "much less interested in reaching an accommodation with the Democrats" on domestic issues.

The confrontation versus legacy issue also is a factor in the administration campaign to win Bork's confirmation. For now, an official said, the plan is to stress Bork's undisputed legal qualifications rather than his conservatism. But he said there is "no guarantee" that Reagan will not try to make the nomination "a national political issue" if it is held up by the Senate.

In his regular radio address this weekend, Reagan urged lawmakers to "keep politics out of the confirmation process" and said, "Judge Bork is recognized by his colleagues and peers as a brilliant legal scholar and a fair-minded jurist who believes his role is to interpret the law, not make it."

Reagan's second-term preference for confrontation emerged when the $87.5 billion highway and mass transit bill reached his desk earlier this year. Baker warned the president that it would be difficult to sustain a veto of the bill, which contained a Reagan-backed provision allowing states to raise the speed limit to 65 mph on rural stretches of interstate highways, but Reagan vetoed it anyway. Congress overrode the veto despite a personal appeal from the president to a group of recalcitrant GOP senators.

Some administration officials say they believe that Reagan's attempt to take the political offensive gives him a chance to raise issues he avoided in the 1984 reelection campaign, when the theme was "It's morning again in America." One administration conservative said, "We're making up for some of the opportunities lost in the reelection campaign and again in this year's State of the Union message."

Reagan's emphasis on conservative themes comes when his White House staff is headed by Baker, usually considered less conservative than either of his two predecessors. During Reagan's first term, when the president compromised more readily than he does now, it was Baker as Senate majority leader who frequently forged deals for him on Capitol Hill.

A senior White House official said Baker came to the White House thinking he could continue to negotiate as he had as majority leader. But the official said Baker has changed his view, realizing that compromise efforts are unlikely to bear fruit with a Democratic-controlled Congress determined to challenge the president. He said Baker also has realized that Reagan is less inclined to negotiate than he used to be.

Baker said when he arrived that one of his priorities was going to be negotiating for Reagan on the budget. Initially, he waited for the Democrats to come up with a budget reflecting their priorities. Then Baker intended to strike a deal on budget revision that would convince Reagan he could negotiate on the merits of the budget, the senior official said.

But the official said the strategy has collapsed because neither the president nor the Democrats are interested in compromise. The senior official said, "Baker could not let {Senate Majority Leader Robert C.} Byrd run it" -- meaning the budget and other issues -- because "the conservatives would eat him alive."

As a result, Baker was said to have acquiesced in the confrontational approach. He was said to have recognized that Reagan was "adamant" against compromise. The official quoted the president as saying, "I've tried and tried and tried" to deal with Congress. "I'm not going to play that game anymore."

In recent weeks, Reagan's confidence has been bolstered by encouraging reports from pollster Richard Wirthlin.

Within the White House there is some defensiveness, however, when aides are asked if Reagan can make headway on Bork or his economic agenda during the coming critical phase of the Iran-contra congressional hearings, when fired national security aide Oliver L. North and former national security adviser John M. Poindexter are scheduled to testify.

When a reporter asked a senior official during a briefing on the "Economic Bill of Rights" whether the presentation was intended as a diversion from the hearings, the aide said anyone who thought that was "out of his mind." He added that Baker and his top aides had mapped out the economic offensive in Santa Barbara, Calif., last April while Reagan was vacationing at his ranch.

White House officials continue to express optimism that Reagan will withstand the North and Poindexter testimony, in part because so many Americans have long ago concluded that the president was not fully telling the truth about the Iran-contra affair.

"We've heard so many things so often that the threshold for shock has been raised," said a senior official. "There is no real fear of being shocked by the testimony."