Republican rivals Tim Pawlenty and Michele Bachmann joust in debate

Republican presidential candidates Mitt Romney (L), Michele Bachman (C) and Tim Pawlenty (Reuters)

Minnesota rivals Tim Pawlenty and Michele Bachmann sparred bitterly in a Republican presidential debate, trying to stand out ahead of an Iowa test vote with huge consequences.

Each seeks to become the main challenger to Republican front-runner Mitt Romney.

In the two-hour, eight-candidate debate, the squabbling by Mr Pawlenty and Mrs Bachmann allowed Mr Romney to remain above the fray and emerge relatively unscathed by his rivals.

Their efforts to earn the right to face President Barack Obama were newly complicated by Texas Governor Rick Perry, who stole some of the spotlight from afar by making it known hours before the debate that he was running for the Republican nomination.

Mr 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.

Seven candidates - Mr Pawlenty, Mrs Bachmann, former Utah Governor Jon Huntsman, former House Speaker Newt Gingrich of Georgia, Texas Representative Ron Paul, former Pennsylvania Senator Rick Santorum and businessman Herman Cain - sought to separate themselves from the packed field and emerge as the chief alternative to Mr Romney.

Though every debate participant assailed Mr Obama, it was clear from the confrontations between Mr Pawlenty, a former Minnesota governor, and Mrs Bachmann, now a member of Congress, who had the most on the line ahead of tomorrow's test vote that could well reduce the field.

Mr Pawlenty, who is struggling to gain traction despite spending years laying the groundwork for his campaign, accused Mrs 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," Mr Pawlenty said.

Mrs Bachmann, who has risen in polls since entering the race this summer and has eclipsed Mr Pawlenty, quickly responded with a list of what she called Mr 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 Mr 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 Mr Romney and his seven rivals each seeking to prove he or she was the strongest Republican to take on Mr Obama.

"I'm not going to eat Barack Obama's dog food," Mr 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 Mr Perry, who was in Texas preparing for a weekend announcement tour to early primary states, and former Alaska Governor Sarah Palin, who is not 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 US credit rating giving Republicans ample opportunities to criticise Mr 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.

Yesterday, he, too, tried to align himself with a public fed up with economic uncertainty and Washington gridlock.

"There is nothing wrong with our country. There is something wrong with our politics," he declared in Michigan, where he was touring an advanced-battery factory.

Mr Pawlenty, who hesitated in a June debate to criticise the former Massachusetts governor, poked at Mr Romney and Mr Obama at the same time.

"Where's Barack Obama on these issues. You can't find his plans on the most pressing issues in this country," Mr Pawlenty said, promising audience members and TV viewers he would "come to your house and cook you dinner" if they could find Mr Obama's proposals.

"Or if you prefer I'll come to your house and mow your lawn ... In case Mitt wins, I'd limit it to one acre."

Mr Romney, who has several homes and was looking to protect his leads in national and state polls, smiled and took a pass when given a chance to respond, saying: "That's just fine."

He kept his focus on Mr Obama, saying: "Our president simply doesn't understand how to lead and how to grow the economy."

He also criticised Democrat Mr Obama on the downgrade of the nation's credit rating.

AP