George W. Bush withstood repeated criticisms from his rivals for the Republican presidential nomination tonight as he joined his five opponents for the first time in a nationally televised campaign debate.

Except for Arizona Sen. John McCain, who was kept busy part of the evening defending his own temperament and lack of support from colleagues in the Senate and at home, all the other rivals took shots at Bush on taxes, Social Security and other issues.

Publisher Steve Forbes was the most aggressive skeptic, starting with a jab at Bush as the "AWOL" candidate who had played hooky at three previous debates. But Forbes also took a strong counterpunch from the Texas governor, who came up with a 22-year-old quote in which Forbes advocated consideration of raising the Social Security retirement age--the same position for which Forbes is criticizing Bush in a new television ad.

Bush, who was questioned by two television journalists on subjects from his environmental record to his aptitude for foreign policy and his reading habits, kept his composure throughout the session. The early favorite for the nomination praised McCain, his closest rival in New Hampshire, retaliated against Forbes and largely ignored the others--Utah Sen. Orrin G. Hatch, talk show host Alan Keyes and conservative activist Gary Bauer.

The criticism was not heated and never grew personal, with the sharpest single exchange occurring between Bush and Forbes on the subject of Social Security. Forbes repeated his ad's claim that Bush's recent statement, refusing to rule out a future increase in the age people begin receiving benefits, was a "betrayal" of a national commitment. Addressing Bush directly, he said, "Governor . . . That's not fair."

Bush replied that he had already made it clear he did not favor boosting the age, now scheduled to rise from 65 to 67, for those nearing retirement age and said he hoped a further rise would not be necessary. Then, turning to Forbes, he quoted from a column his opponent had written for Forbes magazine in November of 1977.

In that piece, Forbes said, "Alas, the unaffordable promises [of Social Security] have to be scaled back, and the best way to do that is to gradually raise the age at which one may collect his full benefits."

When he had a chance, Forbes said it was his view "20 some-odd years ago when the system was in crisis." Today, he said, he favors a transition to private savings accounts that would avoid any increase in the eligibility age.

Forbes hit Bush on every one of his responses, calling the governor's tax cut plan "small," "inadequate" and "convoluted," a plan that would leave the capital gains tax unchanged and the Internal Revenue Service in place. He also criticized Bush for suggesting he might reappoint Alan Greenspan as chairman of the Federal Reserve Board.

It was McCain who teed off on the last point--in the only humorous sally of the evening. The Arizonan said he would not only reappoint Greenspan, but if the chairman were to die, "I'd prop him up and put a pair of dark glasses on him" to preserve his influence on the economy.

But in the early part of the debate, McCain found himself explaining why most of his Senate colleagues and some Republican officials in Arizona are supporting Bush. Denying that his temper had alienated those who have worked with him, he said he had "dear friends" in both parties and the support of 70 percent of Arizona voters in his 1998 reelection race.

But striking the theme that has carried him to near-parity with Bush in New Hampshire polls, McCain proudly proclaimed that lobbyists and special interests know that "if John McCain is president . . . things are going to be a lot different."

Hatch defended McCain's temperament but criticized the Arizonan's trademark campaign finance proposal as one that would leave the Republican Party defenseless against organized labor and the Democrats if it ever became law.

And Hatch used his closing statement to propose that all six of the GOP candidates stump Iowa and New Hampshire together in a two-week bus tour, answering questions from voters every night as a lead-up to the Iowa caucuses on Jan. 24 and the Feb. 1 New Hampshire primary. Hatch said he thought he heard murmurs of agreement from three or four others, but chances of such a tour taking place seemed problematic.

Bauer challenged Bush to join him in pledging to select a running mate who opposes abortion and name only justices who would overturn the Roe v. Wade abortion rights decision, but Bush remained silent on both subjects.

Keyes once again contended that he was the victim of racial bias by the news media, because as a Republican and an opponent of abortion, he is "not in the mold" of "what you folks say is black."

Joining the others in criticizing Bush's tax plan, Keyes also said he did not think people need to "get down on our knees and thank Massa Bush for letting us keep a little more of our money."

Bush remained publicly unrattled by this and other gibes. Defending his tax plan, which has drawn criticism from Democrats and some conservatives, he said: "For some it's not enough. And for some my tax cut is too big. Which leads me to believe I may be doing something just right." He also noted that "I'm the one person up here who has signed a tax cut" into law, adding that he has reduced levies twice as governor of Texas.

The 90-minute debate came as the latest New Hampshire poll showed Bush leading McCain, 41 percent to 36 percent. The Mason-Dixon poll taken Nov. 29-30 and published in today's Concord Monitor also showed a statistical tie on the Democratic side, with Vice President Gore at 45 percent and former senator Bill Bradley at 43 percent.

Forbes led the GOP also-rans, with 7 percent, but he gained the endorsement of the Manchester Union Leader, the state's largest newspaper and an important influence on conservative opinion. While "some would say he looks like a geek," the paper says in Friday's editions, Forbes is "one tough, smart customer" who "can be a strong, principled leader."

Bush had skipped two previous debates in New Hampshire, drawing criticism from his rivals and from some of the state's press. He also was absent from an earlier debate in Arizona, but will debate in Phoenix on Monday night, when the next confrontation among the six contenders is scheduled.

Tonight's panel was notable for an absence of questions on education--an issue that ranks high in the polls--and the paucity of discussion of health care, another burning topic among voters here.

But there was an extended debate on Internet taxation, with most of those who spoke urging that the new avenue of commerce be left untaxed. They took a tentative posture on regulation of Internet content, but most of those who discussed it said "reasonable" restraints were needed on content that could be viewed by children.

Hatch and Forbes took opposite positions on the government's antitrust suit against Microsoft, with the Utah senator saying the Justice Department had presented a strong case and Forbes saying the prosecution was a classic example of overreaching by the Justice Department.

Staff researcher Ben White contributed to this report.