Republican presidential front-runner Newt Gingrich came under sharp and repeated attack here Saturday night, accused by his rivals of being a career politician who has profited by being a Washington insider, a serial hypocrite who has often changed his views and a leader whose intemperate rhetoric can hurt the United States internationally.

The former House speaker, who came prepared for the assault, parried repeatedly as one after another of his rivals aimed criticism at him. He may have been the target, but he defended himself effectively and without losing his composure.

He pointed to his record in government in helping to create jobs in the 1980s and 1990s. He asserted that he has the experience to lead the country and the courage to speak the truth when others equivocate. He was particularly sharp in rebutting former Massachusetts governor Mitt Romney, the biggest threat to his hopes of winning the Republican nomination.

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The debate came at a particularly crucial time in the Republican race, with little more than three weeks before the Jan. 3 Iowa caucuses. The attacks by the other five candidates onstage served to underscore the significance of Gingrich’s rise in national and state polls and the limited time his rivals have to slow his march. The attacks echoed some of what voters in Iowa are seeing on their television screens as the ad wars heat up in advance of the caucuses.

Romney took the lead early in going after Gingrich. Pushed to outline his differences with Gingrich, he ticked off a series of issues, from space exploration to child labor. But he said the biggest difference in their qualifications to be president was in the way they’ve led their lives the past quarter-century.

“We don’t need folks who are lifetime Washington people to get this country out of the mess it’s in,” Romney said. “We need people from outside Washington, outside K Street.”

Gingrich counterattacked. “Let’s be candid,” he said. “The only reason you didn’t become a career politician is because you lost to Teddy Kennedy in 1994. . . . You’d have been a 17-year career politician if you’d won.”

Romney faced some attacks of his own, mostly over his health-care plan in Massachusetts. Texas Gov. Rick Perry was especially aggressive on this issue, and at one point appeared to have tweaked Romney so much over a passage in his book that Romney put his hand out and asked Perry to make a $10,000 bet — a sum of money that drew considerable comment on Twitter as the debate continued — over who was correct. Perry declined to take the bet.

But Romney represented only the leading edge of the criticism aimed at Gingrich in the first candidate debate since he rose to the top of the polls. Rep. Ron Paul (Tex.) accused him of taking money from Freddie Mac at a time when Paul said he was trying to expose the housing bubble, and of being inconsistent in his conservatism.

Rep. Michele Bachmann, who was a consistent critic throughout the debate, and former Pennsylvania senator Rick Santorum then joined in the fray, firing at Gingrich over his record in the House and for supporting an individual mandate in health care.

Perry, trying to resuscitate his campaign, in turn attacked Romney and Gingrich over the individual mandate. Romney said he favored the mandate only for Massachusetts, while Gingrich favored it for the nation. Gingrich said he supported the mandate as an alternative to the health-care plan being advanced by former president Bill Clinton and his wife, Hillary Rodham Clinton, in 1993 and 1994.

The debate covered a wide range of issues, from jobs and the economy to immigration to the Middle East. Along the way, the candidates spoke about what personal issues are relevant to voters’ decisions about the presidency and to the financial strains they have felt in their own lives.

Some of the sharpest exchanges came over Gingrich’s statement in an interview with the Jewish Channel this week in which he described the Palestinians as an “invented” people. The remark drew harsh condemnation from Palestinians and forced Gingrich’s spokesman to issue a modest clarification before the debate.

Paul accused Gingrich of “stirring up trouble” and said the differences between Israelis and Palestinians should be solved by countries in the region. Gingrich responded: “Is what I said factually correct? Yes. Is it historically true? Yes. . . . Somebody ought to have the courage to tell the truth.”

Romney said he agreed with much of what Gingrich had said, except for the phrase “invented” people. He described the words as “incendiary,” adding that he suspected the former speaker would admit he made a mistake. Gingrich shook his head no.

Perry drew strong applause when he shifted the focus to President Obama. “This president is the problem,” he said, “not something Newt Gingrich said.”

Gingrich came under indirect fire on the issue of character, too. Although the candidates did not directly bring up Gingrich’s three marriages, and his being unfaithful to his second wife, Perry said infidelity “sends a very powerful message.”

“Not only did I make a vow to my wife, but I made a vow to God. That’s pretty heavy lifting,” Perry said. “That’s even stronger than a handshake in Texas.”

With Gingrich looking at him sternly, Perry added: “I’m always of the opinion that if you cheat on your wife, you’ll cheat on your business partner.”

Santorum said, “I think character issues do count and I think all of your record, personal as well as political record, is there for the public to look at. I would not say it’s a disqualifier. I would not go that far.”

Gingrich responded that his personal record “is a real issue. ... I think people have to render judgment. In my case, I’ve said up front, openly, I’ve made mistakes at times. I’ve had to go to God for forgiveness.”

Gingrich, 67, said he is now a grandfather and argued that he can be trusted with the presidency. “I am delighted at the way people have been willing to look at who I am, look at what my record has been,” Gingrich said.

Each candidate was asked whether he or she had ever had a personal financial strain that allowed him or her to relate to Americans struggling in the current economy.

“I didn’t grow up poor, and if somebody was looking for someone who grew up in that background, I’m not the person,” Romney said. But he added that he had learned lessons of hard work from a father who grew up poor, and that he helped struggling people as a pastor and leader of his Mormon church outside of Boston.

Paul said he was raised in a modest, Depression-era home, but he turned his focus on the “elimination of the middle class,” which he blamed on the nation’s monetary policy and overspending by the federal government.

Bachmann, meanwhile, sought to root herself in the working class, describing her upbringing by a single mother. “We’re still coupon clippers today,” she said. “We still go to consignment stores today. We get what that feels like. And I think it’s important for the next president of the United States to be in touch with what real people are suffering today, and I have.”

Bachmann also tried to cast Romney and Gingrich as similar in the inconsistency of their conservatism. “If you want a difference, Michele Bachmann is the proven conservative, it’s not Newt-Romney,” she said. “You’ve got to have our nominee as someone who has a stark, distinct difference with President Obama, who can go toe-to-toe.”

On another issue, the candidates divided sharply over whether Congress should extend the payroll tax cut for workers, which expires at the end of the year. Obama has been pushing Republicans in Congress to approve the extension to prevent middle-class Americans from having their taxes raised.

Romney, Gingrich and Paul said they supported it but managed to take swipes at Obama’s stewardship of the economy in their answers. Bachmann, Perry and Santorum said they opposed the extension.

“I’m completely different from Barack Obama on this issue,” Bachmann said. “We have candidates on this stage who are standing with Barack Obama on this issue.”

Romney and Gingrich reprised an earlier clash over immigration and what to do with about 11 million people who are in the country illegally. Gingrich said he favored making it possible for those who have been here for 25 years or more and have deep roots in their communities to become permanent residents, though not citizens. Romney said he thought that would create incentives for a new wave of illegal immigration.

The debate, the 12th this year among the Republican candidates, was the first since businessman Herman Cain suspended his campaign, and came at a time of dramatic change in the race. The debate was sponsored by ABC News, the Des Moines Register, Yahoo News and the Iowa Republican Party. ABC’s George Stephanopoulos and Diane Sawyer served as moderators.

Gingrich was on the spot heading into the debate, having zoomed into the lead in the polls. A recent round of polls, including one by The Washington Post and ABC News, showed Gingrich with a double-digit lead over Romney and Paul, who were tied for second. But he is behind Romney and Paul in building an organization to turn out his supporters on caucus night.