The polite Republican presidential race exploded in anger tonight against presumed front-runner George Bush about the issue of who had the right to debate him three days before the New Hampshire primary.

Four other GOP contenders of various ideological stripes joined Ronald Reagan in condemning Bush and the Nashua Telegraph for insisting that Reagan alone be allowed to debate Bush before an excited audience of 2,000 in the Nashua High School gymnasium.

Bush's campaign manager, James A. Baker III, said the extraordinary protest was "a set-up" and showed that "it's stop-George Bush" time in the GOP contest.

Reagan scored repeated debating points off Bush in the 90-minute confrontation, while the other four, Sens. Howard H. Baker Jr. and Bob Dole and Reps. John B. Anderson and Philip M. Crane, had to content themselves with being introduced at the beginning and allowed to make brief statements at the end.

Off stage, the four jilted contenders denounced Bush even more than they did the newspaper that conceived the one-on-one encounter. "Clearly the responsibility for this travesty is on Bush," Anderson said. He charged that "any man seeking the highest office in the land . . . would show that kind of arrogance before the first primary in the nation" is almost unthinkable.

Baker, angrier than many reporters had ever seen him, called it "the most flagrant effort" to stifle debate. "It is an effort to reinstitute closed-door policies."

Baker and the others charged that Bush had refused to meet with Reagan and the rest of them to discuss Reagan's efforts to open the debate. "If he is the front-runner," Baker said, "he wears that crown most unbecomingly."

Dole said, "George Bush torpedoed us tonight . . . He had better find himself another party." Dole said that he told Bush as he was leaving the stage, "There'll be another day, George."

Crane said, "I wouldn't lend one iota of legitimacy to this fraud."

The four said they would work to deprive Bush of the GOP nomination, but they stopped short of saying they would back any other candidate or organize a stop-Bush effort. Baker summarized the views of his colleague competitors when he said, "If George Bush is the nominee, I support (him), but I will do everything I can to see that does not happen."

The Bush campaign was taken aback by th stormy reaction. Bush told the audience in the gymnasium that he had been challenged to the debate by Reagan and accepted the invitation of the local newspaper, the Telegraph. "I've been invited here as the guest by the Nashua newspaper," he said, "and I will play by their rules."

His campaign manager, James A. Baker III, said he had told the others that "It wasn't our call -- it was the Telegraph's call."

Asked why Bush had refused to meet the other candidates, James Baker said, "That would have been somewhat unwise. It was five against one."

Within the gymnasium, the scene was stormy. The crowd, alternating in cheers of "We Want Reagan," and "Bush, Bush," had waited for the debate to begin for 40 minutes past the scheduled time, with many members of the audience obviously not aware of the negotiations delaying the process.

Bush came in first, smiling. He was followed by an obviously angry Reagan and the four other candidates, who remained standing awkwardly behind the desk where the two invited debaters and Nashua Telegraph executive editor Jon Breen, the moderator, were seated.

When Breen announced it would remain a two-man debate, Reagan attempted to explain how he had wanted to include the other candidates.

"Will you please turn off Gov. Reagan's microphone?" Breen said.

"I'm paying for this microphone," Reagan responded, and went on to make an empassioned speech about why he had invited the other candidates to join him and Bush.

Reagan's comment was a reference to the fact that his campaign organization agreed to pay the $3,500 cost of renting the high school, after the Federal Election Commission ruled that it would be an illegal corporate contribution for The Nashua Telegraph to finance a debate from which most of the Republican contenders were excluded.

When Reagan finished his talk, even some Bush partisans were applauding him and the four shunned candidates were waving to the crowd. As they left the stage, Reagan shook the hands of each of the, while Bush remained seated, waiting for the formal proceedings to begin.

Reagan was like a man aroused. Somewhat passive in his first debate Wednesday night, he completely dominated tonight's debate, punctuating his comments with one-liners and frequently putting Bush on the defensive.

When the 69-year-old Reagan was asked whether he believed in mandatory retirement at 70, he replied, to laugh, "Don't you think there's a conflict of interest here?" Then he said government should not be dictating anyone's retirement age.

When Bush was asked whether he thought Reagan was too old to be president, and replied in the negative, Reagan responded, "I agree with George Bush."

Reagan said that Bush's proposal for a $20 billion federal tax cut would leave a $21 billion tax increase, because inflation would move many taxpayers into higher brackets.

Bush was peppered with questions about his 1968 vote restricting mail-order gun sales and about allegations that he failed to report contributions given him in 1970 from a secret fund organized at President Nixon's direction.

The "slush fund" question provoked Bush's most eloquent moment of the evening. He said, with some heat, that he had reported everything as far as he was aware and would have been proud to claim a contribution from Nixon at the time.

"My record in public life has been one of total integrity and honor," Bush said.

This answer produced applause, but the loudest applause of the evening -- a full minute, which moderator Breen interrupted with a threat to close the debate -- came when Reagan answered a question about what he would do to help Vietnam war veterans who had been harmed by a defoliant known as "Agent Orange."

"We owe them an apology for the way they have been treated . . . and we must give them a promise never to let them fight and die for a war their government will never let them win," Reagan said.

Bush said the government should investigate and "make the proper settlement."

Although the substance of the debate was overshadowed by the off-stage and preliminary fireworks, Bush and Reagan broke new grounds in some areas and defined their differences more clearly than they had before.

Reagan, for the first time, said that "the time has long since past" when a deadline should be set for release of American hostages in Iran. While acknowledging that he was not certain what form retaliation should take, he said the U.S. government should tell Iranian authorities, "Turn them over to us as of this date, or something is going to happen."

While Bush confessed to a "mounting frustration," over the delay in the hostages' release, he reaffirmed his support of President Carter's policies, saying, "There is no simple answer" to gaining their freedom and, meanwhile, there is the advantage of preserving their lives.

Bush was pressed to explain a recent newspaper interview some had interpreted as saying that he believed the United States could base its policy on surviving a nuclear war. He said flatly, "It is not possible . . . The way to win it is to deter it, by keeping the country strong," Bush said.

Reagan said the Soviets are operating on the premise that a nuclear war is winnable, but said the danger of such a war is not imminent because the Soviets are moving toward strategic superiority but have not yet achieved it.

Both men ruled out the use of tactical nucear weapons in the Persian Gulf.

Bush said the security of the region depends on "reversing the decline" in U.S. conventional forces, and Reagan said the United States could make the Soviet Union "retreat a little, by putting a blockade around Cuba until they remove their troops from Afghanistan."

Both candidates were heavily applauded for their emotional closing statements, which were excerpted from their basic stump speeches. But afterward, at post-debate news conferences, they were peppered with questions about their pre-debate conduct.

Reagan and his press secretary, Jim Lake, said they had called the paper during the day because they did not want the onus of sponsoring a debate which the Federal Election Commission had found unfair. Reagan said he became concerned because he was, in effort, sponsoring the debate by paying its cost.

When Lake called a Bush aide to say he was "caving" on the issue, Bush campaign chairman Baker interpreted this as a sign that Reagan wanted to pull out entirely.

Apart from the merits of this dispute, there was a general feeling among camp followers of both sides that Reagan had profited from becoming angry.

"It really got the adrenalin flowing . . . which was just what we needed," said Reagan's New England coordinator, Gerald Carmen.

Reagan was asked what effect he thought the debate would have, and replied, "The only thing I can think of is that I probably won't get a helluva lot of attention from the [Nashua] newspaper."