“She speaks of leading these [conservative] efforts in Washington and Minnesota,” Pawlenty lashed out. “Leading and failing is not the objective.”

Bachmann assailed Pawlenty with a litany of alleged deviations from conservative orthodoxy, blasting: “When you were governor, you implemented cap-and-trade in our state and you praised the unconstitutional individual mandate.

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

The caustic exchanges were no accident: A defeat on Saturday could snap Bachmann’s momentum in the race, or seal Pawlenty’s fate as a 2012 also-ran.

For the race beyond the straw poll, however, neither the candidates nor the moderators did much to draw blood from national front-runner Mitt Romney, who sauntered unscathed through his second consecutive debate.

The questions from Fox News and the Washington Examiner lobbed potentially difficult questions at Romney, asking him to defend his record on taxes in Massachusetts and his near-absence from the recent debate over whether to raise the federal debt ceiling.

On both issues, Romney stuck to narrow talking points, declaring that his support for the conservative Cut, Cap and Balance pledge told voters all they needed to know about his views on the debt ceiling.

Asked about a presentation his administration once gave to Standard & Poor’s, saying that Massachusetts deserved a credit rating upgrade in part because it raised taxes, Romney sidestepped the issue entirely.

Romney was barely challenged on his carefully parsed answers. With Pawlenty and Bachmann focused on each other, and several of the other candidates flailing in their attempts to stand out from the crowd, Romney took little heat from his fellow Republicans.

Indeed, virtually all of the candidates helped confirm — in one form or another — that Romney will likely face a tougher political challenge from a late-announcing candidate like Texas Gov. Rick Perry than from any of his currently declared rivals.

With the exception of raucous back-and-forths between Rick Santorum and Ron Paul on Iran and marriage, they did little to capture the spotlight.

Jon Huntsman, who was making his first performance in a 2012 presidential debate, fell short of his campaign’s recent promises that he would take a more aggressive approach to delivering his message to draw contrasts with his rivals. On Thursday night, the former Utah governor delivered only the softest and most implicit of criticism of his opponents, alluding to candidates who want to “run from their record,” in an apparent reference to Mitt Romney.

For the most part, Huntsman spoke softly and carried an exceedingly well-mannered set of talking points reminiscent of the civil campaign he promised when he launched last month.

None of the other candidates seemed to have a moment on stage to give them an extra head of steam going into the straw poll, though Paul drew repeated rounds of applause from his enthusiastic fans as he delivered his distinctive libertarian message.

Perhaps the most memorable moment of the night — outside the Bachmann-Pawlenty blowups — wasn’t instigated by a candidate at all, but rather by Byron York.

The Washington Examiner columnist queried Bachmann about a story she once told, relating how she decided to become a tax lawyer at her husband’s urging, out of a belief that wives should be “submissive” to their spouses.

Would Bachmann, York asked, be submissive to her husband if she were president?

Bachmann paused as a murmur ran through the crowd, and then began her answer: “Thank you for that question, Byron.”

“Marcus and I will have been married for 33 years this Sept. 10,” Bachmann said, explaining that to her and her husband, being submissive “means respect.”

“I respect my husband,” she said. “And he respects me as his wife. That’s how we operate our marriage. We respect each other. We love each other.”

Gingrich, too, won a moment of applause by pushing back at the moderators, in a blunter way than Bachmann.

Asked for the umpteenth time to explain the mass exodus of campaign staffers in June by Fox’s Chris Wallace, the former House speaker fumed: “I took seriously [Fox anchor] Bret [Baier]’s injunction to put aside the talking points. I wish you would put aside the gotcha questions.”

At times, Gingrich displayed the kind of fluency with issues that earned him a reputation as the GOP’s ideas man. He cut the professorial, wonky profile he cultivated for years before deciding to seek the White House, seeming closer to finding a comfortable role for himself in the 2012 field.

Still, overshadowing the whole debate was anticipation of a new strong candidate — Perry — entering the 2012 field Saturday.

And as the moderators noted, at least two other prominent Republicans, Sarah Palin and Rudy Giuliani, have not ruled out campaigns of their own. Palin is scheduled to visit the Iowa State Fair on Friday.

The candidates professed indifference at the prospect of new competition.

“Welcome to the contest,” Herman Cain said when he was asked about a potential Perry campaign. “From my perspective, it doesn’t bother us or my campaign. That’s just one more politician and that makes this business problem solver stand out that much more.”