"Look, she has done wonderful things in her life -- absolutely wonderful things -- but it is an undisputable fact that in Congress her record of accomplishment and results is non-existent," Pawlenty said of Bachmann in the 2-hour nationally televised debate.
"When you were governor in Minnesota, you implemented 'cap and trade' in our state, and you praised the unconstitutional individual mandates and called for requiring all people in our state to purchase health insurance that the government would mandate," Bachmann retorted. "You said the era of small government was over. That sounds more like [President] Barack Obama, if you ask me."
The back-and-forth continued, but Pawlenty, who has lagged behind in national public-opinion polls, also jabbed front-running former Massachusetts Gov. Mitt Romney on his record and mocked his wealth.
Pawlenty at one point challenged viewers to find any specific Obama plan for fixing Social Security, Medicare and other issues.
"If you can find Barack Obama's specific plan on any of those items, I will come to your house and cook you dinner," he said to loud applause, saying he was also willing to mow the winner's lawn.
Then, in a dig, he said if Romney won, "I will limit it to one acre."
Pawlenty criticized the Massachusetts healthcare-reform legislation Romney signed in 2006 as a model for the national reform passed under Obama. Conservatives deplore the national reform as a government takeover.
Romney said in response: "We put together a plan that was right for Massachusetts. The president took the power of the people and the states away from them and put in place a one-size-fits-all plan."
Romney was asked about his statement to the Standard & Poor's Corp. credit-rating firm that during his time as governor, Massachusetts raised taxes and closed tax loopholes.
Romney said: "I don't believe in raising taxes. And as governor, I cut taxes 19 times and didn't raise taxes."
The third formal debate of the campaign took place at Iowa State University two days before the Ames Straw Poll, a state party fundraiser also at the university.
The poll -- described as a cross between a political convention and a county fair -- has been an uncertain predictor of which candidate will prevail.
The debate also marked the first appearance onstage by former Utah Gov. Jon Huntsman Jr., a former ambassador to China under the Obama administration.
Huntsman pointed out he was the only presidential hopeful to support the debt-ceiling deal worked out by Obama and congressional Republicans.
"We are 25 percent of the world's [gross domestic product]," Huntsman said, saying the idea of letting the country default was unthinkable to him.
Other hopefuls debating included Rep. Ron Paul of Texas, former Sen. Rick Santorum of Pennsylvania, former Godfather's Pizza Chief Executive Officer Herman Cain and former House Speaker Newt Gingrich.
Not participating was openly gay candidate Fred Karger, who claims he met the Fox News Channel criteria but was disallowed.
Two GOP figures also not represented -- Texas Gov. Rick Perry, whose office confirmed Thursday he would enter the race Saturday, and former Alaska Gov. Sarah Palin, who was to be in Iowa Friday and promised to say by next month if she intends to run.
Bachmann was asked by FNC "Special Report" host Bret Baier if Palin's Iowa visit would steal her thunder.
"I like Sarah Palin a lot," Bachmann said. "We are very good friends. And I think there's room in the race for Gov. Perry, Sarah Palin or even, Bret, you too, if you want to throw your hat into the race."
Gingrich jousted with "Fox News Sunday" host Chris Wallace -- a former colleague of Gingrich's at FNC, who asked why Gingrich's campaign "has been a mess so far."
Gingrich accused Wallace of "playing Mickey Mouse games" and asking "gotcha" questions.