Jim O’Toole, Post Gazette

SIOUX CITY, Iowa — The Republican presidential contenders took advantage of the biggest remaining spotlight before real votes are cast to make, for the most part, high road appeals to the caucus goers who will assemble across this state in just 16 days.

The sharpest clashes Thursday night came between Texas Rep. Ron Paul and Minnesota Rep. Michele Bachmann over his outspokenly non-confrontational attitude toward Iran.

Ms. Bachmann was also on the attack against former House Speaker Newt Gingrich, as she pressed him anew on the $1.6 million in consulting fees he had earned from the mortgage lender Freddie Mac.

But the clashes between front-runners Mitt Romney, the former Massachusetts governor, and Mr. Gingrich, which enlivened their last debate and were amplified on the campaign trail this week, were absent.

Mr. Romney was able to project, unchallenged by his rivals, the self-portrayal of a businessman whose private sector experience would allow him to right the economy.

“I know what it takes to get this economy going; the president doesn’t,” he said.

Mr. Gingrich, whose ascendancy has reshaped the race in the last month, struck the civil tone from the first question, offering holiday greetings to the crowd before parrying a question on whether he was too controversial and volatile to defeat President Barack Obama.

He portrayed himself as a figure with big ideas who understands the economy and would leave the president “without a leg to stand,” defending his record in general election debates.

In the second half of the debate, however, Ms. Bachmann returned to a line of attack from the previous debate as she criticized Mr. Gingrich sharply on his consulting contract. Mr. Gingrich insisted that he had never lobbied anyone or changed any position because of a business relationship.

Ms. Bachmann, battling for the votes of social conservatives, also challenged the former speaker over the fact that he had once said that he would not work against Republican lawmakers who had not supported the ban on partial birth abortion.

Abortion was also at the center of a question to Mr. Romney over whether he had changed his position on that and other issues over the years as a matter of political expediency.

Former Pennsylvania Sen. Rick Santorum professed to be unconcerned about his lagging poll numbers, insisting that, “I’m counting on the people of Iowa to catch fire for me.” He called himself the true consistent conservative in the race.

Mr. Gingrich defended his conservative credentials.

Texas Gov. Rick Perry likened himself to Denver Broncos phenom Tim Tebow as he defended his sometimes shaky performances in past debates and said he was ready to play on the presidential stage. His performance Thursday night, if not memorable, was free of the gaffes that have sometimes marred previous appearances.

Former Utah Gov. Jon Huntsman boasted of his record in establishing a pro-business climate as governor.

As the candidates gathered for the debate, at least two new polls suggested that the Gingrich candidacy was in jeopardy of following the same trajectory as others among the GOP’s rotating front-runners this year. His Iowa lead had fallen sharply in one and he was actually trailing in another after days in which he was the target of tough commercials and criticisms from his rivals.

If the field’s collective nerves were on edge, it was understandable, just 16 days before a contest that still appears up in the air.

A Public Policy Polling survey released this week found Mr. Gingrich still in first place, but by a sharply reduced margin than he had in a PPP snapshot two weeks ago. Rasmussen Reports showed an even steeper slide for the former speaker, his 32 percent to 19 percent lead over Mr. Romney last month flipping to a three-point deficit: Mr. Romney, 23 percent; Mr. Gingrich, 20 percent.

The PPP survey showed Mr. Paul at 21 percent, in a virtual tie with Mr. Gingrich, followed by Mr. Romney, 16 percent; Ms. Bachmann, 11 percent; Mr. Perry, 9 percent; Mr. Santorum, 8 percent; and Mr. Huntsman, 5 percent.