Ames, Iowa ? Minnesota rivals Tim Pawlenty and Michele Bachmann sparred bitterly Thursday night during an eight-candidate Republican debate, trying to break out of the GOP presidential pack ahead of an Iowa test vote with huge consequences. Each seeks to become the main challenger to Republican front-runner Mitt Romney.

Romney, a multimillionaire businessman who casts himself as a jobs creator, made his own stir earlier in the day when, at the Iowa State Fair, he declared that “corporations are people,” drawing ridicule from Democrats.

Those were just the latest twists in the most consequential week yet in the 2012 Republican presidential nomination fight.

In the two-hour debate, the squabbling by Pawlenty and Bachmann allowed Romney, the GOP front-runner making his second presidential bid, to remain above the fray and emerge relatively unscathed by his rivals.

Though every debate participant assailed President Barack Obama, it was clear from the confrontations between Pawlenty, a former Minnesota governor, and Bachmann, now a member of Congress, who had the most on the line ahead of Saturday’s straw poll that could well winnow the field.

On stage just a few minutes, Pawlenty, who is struggling to gain traction despite spending years laying the groundwork for his campaign, accused Bachmann of achieving nothing significant in Congress, lacking executive experience and having a history of fabrications.

“She’s got a record of misstating and making false statements,” Pawlenty said.

Bachmann, who has risen in polls since entering the race this summer and has eclipsed Pawlenty, quickly responded with a list of what she called Pawlenty’s liberal policies when he was Minnesota’s governor, including his support for legislation to curb industrial emissions.

“You said the era of small government is over,” she told Pawlenty. “That sounds a lot like Barack Obama if you ask me.”

Much of the rest of the debate was heavily focused on the Democratic incumbent, with Romney and his seven rivals each seeking to prove he or she was the strongest Republican to take on Obama.

“I’m not going to eat Barack Obama’s dog food,” Romney said when asked whether he would have vetoed the compromise legislation that Congress gave to the president that raised the debt ceiling. “What he served up is not what I would have done if I’d had been president of the United States.”

Notably absent from the eight-candidate spectacle were Texas Gov. Rick Perry, who was in Texas preparing for a weekend announcement tour to early primary states, and former Alaska Gov. Sarah Palin, who isn’t a candidate but was stoking presidential speculation anew with a visit to the Iowa State Fair.

The nation’s teetering economic situation shadowed the debate, with stock market volatility and a downgrade in the U.S. credit rating giving Republicans ample opportunities to criticize Obama.

The Democratic president will get his shot to counter the criticism next week during a Midwestern bus tour that will take him through this state that helped launch him on the path to the White House four years ago.

But in Iowa Thursday night, the Republicans commanded the spotlight.