Republican presidential hopefuls are introduced Tuesday at the Ford Community and Performing Arts Center in Dearborn Mich. Shown are, from left, Ron Paul, Mike Huckabee, John McCain, Mitt Romney, Fred Thompson, Rudy Giuliani, Duncan Hunter, Sam Brownback and Tom Tancredo.

Dearborn, Mich. ? Republican presidential hopefuls Mitt Romney and Rudy Giuliani quarreled over tax and spending cuts Tuesday, each claiming greater commitment than the other in a debate in the nation’s struggling manufacturing heartland.

The government “is spending money of future generations and those yet to be born,” added Fred Thompson, making his debut on a debate stage after a late entry into the race. He said future retirees should receive smaller Social Security benefits than they have been promised.

After months of polite debate sparring, Giuliani and Romney squared off without hesitation, a reflection of their struggle for primacy in the race for their party’s presidential nomination.

“I cut taxes 23 times. I believe in tax cuts,” said Giuliani, former mayor of New York and leader in national Republican polls.

Romney initially conceded that, but quickly criticized his rival for once filing a court challenge to a law that gave President Clinton the right to veto spending items line by line. “I’m in favor of the line-item veto,” he said, adding he exercised it 844 times while governor of Massachusetts.

Romney also said that while mayor, Giuliani “fought to keep the commuter tax, which is a very substantial tax … on consumers coming into New York.”

The former governor leads his rivals in the polls in Iowa, where caucuses will be the first contest of the campaign, and he and Giuliani are in a close race in surveys in New Hampshire, the leadoff primary state.

Giuliani responded that spending fell in New York while he was mayor, and rose in Massachusetts while Romney was governor.

“The point is that you’ve got to control taxes. I did it, he didn’t. … I led, he lagged.”

“It’s baloney,” retorted Romney. “I did not increase taxes in Massachusetts. I lowered taxes.”

The exchange was among the most heated of the campaign for the Republican presidential nomination, reflecting a quickening pace as the 2008 caucuses and primaries draw close.

It also left Thompson, Sen. John McCain of Arizona and the other contenders as something of bystanders for the several moments that Romney and Giuliani went at one another.

All nine of the men on stage sought to stress their conservative economic credentials throughout the two-hour debate, held in the city that gave birth to the Ford Motor Co. more than a century ago.

McCain of Arizona said President Bush was right to veto a children’s health expansion bill, and he urged him to reject a multibillion-dollar public works measure as well.

“We’ve got to get wasteful spending under control,” he said.

“We have to get spending under control,” agreed Kansas Sen. Sam Brownback. No matter whether Republicans or Democrats are in control of Congress, he said, “the system is built to spend.”

Challenged to identify one government account he would cut, Brownback cited a program involving “advanced technology.”

“If you want to control federal spending you must look at Social Security and Medicare,” said Rep. Tom Tancredo of Colorado. He said he favors private Social Security accounts, or “forget the idea of ending deficit spending.”

Thompson said that without changes, Social Security would not survive. He said there should be no change for current retirees and those expected to begin drawing benefits soon. But for those retiring further in the future, benefits should not be allowed to rise as quickly as now expected.

While maneuvering against one another, the Republicans found a minute or two to jab at Democrats.

Giuliani criticized Sen. Hillary Rodham Clinton, the Democratic presidential front-runner, for a proposal to provide tax cuts of up to $1,000 to help families open 401(k) retirement accounts.

“Hillary is filled with endless ways to spend. We’re going to have to control that,” he said.

Romney criticized Michigan Gov. Jennifer Granholm for raising taxes, and drew laughter when he said he was afraid she “was going to put a tax on this debate.”

Eight of the candidates support the continuing U.S. military presence in Iraq, but Rep. Ron Paul of Texas drew applause when he loudly dissented. Paul posted a surprising $5 million in campaign donations for the three months ending Sept. 30.