The GOP candidates debated in Iowa on Sunday.

DES MOINES (CNN) — It was no holds barred Sunday as the Republican presidential hopefuls took part in the first Iowa debate of the 2008 elections.

In a 90-minute session broadcast live on ABC's "This Week," the nine official GOP contenders clamored for support in the state that chooses among them first in the election cycle.

They targeted each other's positions on abortion, shared ideas for protecting the nation's infrastructure in the wake of the Minneapolis bridge collapse, and, in some cases, offered criticisms of President Bush.

The most dramatic moments came when former Massachusetts Gov. Mitt Romney came out swinging against Sen. Sam Brownback of Kansas, whose campaign had sponsored an automated phone message to Iowans. That advertisement skewered Romney's changed position on abortion, saying he had pledged to uphold policies legalizing abortion before declaring himself opposed to them.

"I am pro-life. And virtually every part of that ad is inaccurate," said Romney.

Brownback noted Romney's previous stance, which he expressed years ago in a video that is currently viewable on YouTube.

"I get tired of people that are holier than thou because they've been pro-life longer than I have," Romney said.

Brownback vowed that, if elected president, he would appoint a Supreme Court justice who, "I hope, would be the voting decision to overturn Roe v. Wade."

Former New York Mayor Rudy Giuliani, who supports abortion rights, was called on to defend his position.

"I believe the best way we can have common ground in this debate that you're hearing is if we put our emphasis on reducing abortions and increasing the number of adoptions, which is something that I did as mayor of New York City," he said. "But I think ultimately that decision that has to be made is one that government shouldn't make. Ultimately, a woman should make that with her conscience and ultimately with her doctor." Fix infrastructure through taxes?

Since last week's bridge disaster in Minneapolis, state governments and the federal government have begun efforts to ensure such infrastructure is safe. State and federal officials say the needed efforts would require federal funds. The presidential hopefuls agreed, however, a tax hike was not the answer.

"We should put more money into infrastructure. We should have a good program for doing it. But the knee-jerk liberal Democratic reaction — raise taxes to get money — very often is a very big mistake," said Giuliani. He said that, as mayor of New York City, he raised money for capital improvement projects through a tax cut that ultimately generated more revenue. The mayor said such moves helped cut the number of "poor bridges from 5 percent to 1.7 percent."

Romney drew a similar picture, saying the "biggest source" of funding is growing the U.S. economy. Also, he said, "We have to reorient how we spend our money."

Citing pork-barrel spending, he said that in Massachusetts, "Instead of spending it to build new projects — the bridge to nowhere, new trophies for congressmen — we instead said, 'Fix it first.'"

Former Arkansas Gov. Mike Huckabee said, "We're spending billions of dollars all over our country and around the world, but it may be time that we start spending some of those billions of dollars to deal with our own infrastructure."

Noting last month's steam pipe explosion in New York as another example of crumbling infrastructure, he said, "We have to start addressing building this country, not everybody else's."

Sen. John McCain, R-Ariz., said Congress shares blame for problems with the nation's bridges and roads. "We passed a $50 billion transportation bill that had $2 billion in pork-barrel, earmarked projects," he said. "Not one dime in those pork-barrel projects was for inspection or repair of bridges." What would you restore?

The candidates were shown a clip of President Bush in 1999 promising to "restore honor and dignity to the Oval Office."

Asked what they would restore, Rep. Tom Tancredo, R-Colo. answered, "Hope — hope in America itself, remembering that we have made a number of mistakes that have turned our friends against us, have encouraged our enemies."

Giuliani too vowed to restore hope.

Former Wisconsin Gov. Tommy Thompson said he would restore bipartisanship to the White House — by opening "the East Wing … to bring in the best minds — Democrats, Republicans, independents across America — that want to get something done with this great country."

McCain and Giuliani each argued that their experience separates them from the pack.

"I am fully prepared — fully prepared, more than anyone else running on either side — to fight the transcendent challenge of this nation, which will be for all of the 21st century. And that is the struggle against radical Islamic extremism," said McCain, citing his military background.

"We must win. We will win. And we will never surrender; they will."

Giuliani, speaking next, said, "In deference to the senator, I think the senator is a great man and very well-qualified." He went on to emphasize something that distinguishes him from McCain — though Giuliani expressed it as something that distinguishes him from "the three leading Democratic candidates.

They haven't held an executive office in their lives. They haven't run a city, a state, a business … You've got to have some kind of experience for this job."

On the question of Iraq, Rep. Ron Paul of Texas stood out as the maverick of the group, repeating his call for an immediate exit. "We went in illegally and we ought to just come home!" he said to applause.

McCain has said his support for President Bush's troop increase policy cost him support among independents. But in Sunday's debate he reiterated his assertion that the plan is bringing about improvement.

The war "was very badly mismanaged for nearly the first four years. I was one of the greatest critics," McCain said. "We do now have a strategy that is succeeding. We do have a military whose morale is up because they see this success."

Rep. Duncan Hunter, R-Calif., said the United States is "standing up" Iraq's military. Once the Iraqi forces are "reliable, battle-ready," they will displace U.S. heavy combat forces, he said. "That's the right way to leave, not a stampede for the exit."

Several candidates weighed in on Sen. Barack Obama, D-Ill., a leading presidential candidate, for saying last week that he would consider taking military action in Pakistan unilaterally. "If we have actionable intelligence about high-value terrorist targets, and President Musharraf will not act, we will," Obama said. The remark drew rebuke from some fellow Democrats, including presidential hopeful Sen. Hillary Clinton of New York.

Giuliani said, "I believe that is an option that should remain open. I believe the senator didn't express it the right way. I think the senator, if he could just say it over again, might want to say that we would encourage Musharraf to allow us to do it if we thought he couldn't accomplish it."

Romney had harsher words for Obama. "I think Barack Obama is confused as to who are our friends and who are our enemies," he said.

"We do not go out and say to a nation, which is working with us, where we have collaborated and they are our friend and we're trying to support Musharraf and strengthen him and his nation, that instead that we intend to go in there and potentially bring out a unilateral attack," he added.

In answer to a question about Vice President Cheney, Brownback inserted criticism of Bush. "I think Dick Cheney has done an admirable job," said Brownback. "I think the president's over-relied upon that."

All the candidates sought to distinguish themselves from Bush, who faces low popularity ratings. "I'm not a carbon copy of President Bush, and there are things I would do that would be done differently," said Romney. But, he added, "I know they make mistakes. But they have kept us safe these last six years. Let's not forget that."