WASHINGTON (AP) — The final Republican presidential debate before the Jan. 3 Iowa caucus crystalized the strengths and weaknesses of the chief contenders as perhaps no other event thus far.

It reinforced the notion that this is a battle between Mitt Romney and Newt Gingrich unless one of the other five can make a dramatic late run.

Given his likely strength in the Jan. 10 New Hampshire primary, Romney may be able to survive a so-so finish in Iowa. It appears more important for Gingrich to win Iowa, or come close, and Thursday's two-hour televised debate in Sioux City probably helped his cause.

It wasn't so much that the former House speaker had a solid second hour after a somewhat shaky start. It's more that Rep. Ron Paul, the libertarian-leaning Texan, expressed his anti-war, anti-interventionist views so vehemently that he may have turned off mainstream Republicans who otherwise might have helped him to a surprising first-place finish.

"To declare war on 1.2 billion Muslims and say all Muslims are the same, this is dangerous talk," Paul said of the idea of taking pre-emptive action to prevent Iran from developing nuclear weapons. "Yeah, there are some radicals. But they don't come here to kill us because we're free and prosperous ... They want to do us harm because we're bombing them."

Rep. Michele Bachmann said, "I have never heard a more dangerous answer for American security."

If Paul hurt himself among rank-and-file GOP voters, then Bachmann, Texas Gov. Rick Perry and former Sen. Rick Santorum may have helped themselves with solid performances. Bachmann, who faded after winning a mid-August straw poll in Iowa, was especially forceful in accusing Gingrich of being soft on abortion and hypocritical for taking big consulting fees from mortgage giant Freddie Mac while criticizing its work.

Perry, whose campaign faltered after several weak debate performances, showed humor and a command of several topics. The big question is whether any of these second-tier candidates — and conceivably, former Utah Gov. Jon Huntsman — can gain the needed traction that has eluded them for months.

As for Romney and Gingrich, the feisty debate on Fox News laid bare their biggest strengths and vulnerabilities.

Romney, the former Massachusetts governor, once again managed to stay above most quarrels. He seemed well prepared for a challenge to his job-creation record. Romney acknowledged that some jobs were eliminated in corporate restructurings he oversaw at Bain Capital, but the overall effort "added tens of thousands of jobs."

However, Fox News' Chris Wallace, with help from Santorum, bore in on Romney's biggest liability: his changed positions on gun control, gay rights and particularly abortion.

Romney gave his standard response about having a change of heart regarding his former support for abortion rights.

He then got drawn into a complicated back-on-forth about what he meant when he vowed in 1994 to be a better defender of gay rights than Sen. Ted Kennedy, D-Mass., whom he was trying to unseat.

Later, when he was governor, Romney said, the state's highest court "determined that under our constitution, same-sex marriage was required." It wasn't up to him, he said, "to make a choice as to whether we had it or not."

Romney said he fought "to overturn the court's decision" and make marriage "between a man and a woman."

A similarly testy exchange underscored Gingrich's greatest vulnerability: his long, contentious record in Washington, which included some prominent deal-making with Democrats during his 20 years in Congress.

Gingrich rejected the notion that he's an unreliable conservative. He said he pursued conservative but attainable goals, working when necessary with Democrats such as President Bill Clinton and Speaker Tip O'Neill.

"The term 'government-sponsored enterprise' has a very wide range of things that do a great deal of good," Gingrich said, defending his $1.6 million consulting fee for Freddie Mac. "There are a lot of very good institutions that are government-sponsored."

Such comments wouldn't raise eyebrows among independent or Democratic voters. But they may open Gingrich to questions from the staunch conservatives who dominate GOP caucuses and primaries.

Republican consultant Alex Castellanos said via Twitter there will be "zillions of negative ads still dropping on Newt's head in Iowa after this debate."

Gingrich also displayed several flashes of the bravado that strikes some people as brilliance, others as arrogance. A former college professor who used deferments to avoid the draft during the Vietnam War, Gingrich said he spent "23 years teaching one- and two-star generals and admirals the art of war."

Condemning what he sees as liberal activism by federal judges, Gingrich said, "I testified in front of sitting Supreme Court justices at Georgetown Law School, and I warned them: 'You keep attacking the core base of American exceptionalism, and you are going to find an uprising against you which will rebalance the judiciary.'"

"Just like Jefferson, Jackson, Lincoln and FDR," he said, "I would be prepared to take on the judiciary, if in fact it did not restrict itself in what it was doing."

Republican voters in Iowa and New Hampshire have surprised the nation before. At this stage four years ago, many saw Rudy Giuliani as the likeliest GOP nominee.

Perhaps Perry, Bachmann or Santorum will make an 11th hour surge. Maybe Paul drew more fans than he turned off with his isolationist talk Thursday.

But with little more than two weeks left before the Iowa caucus, most are watching to see if Romney and Gingrich can make the most of their strengths and minimize their weaknesses.


EDITOR'S NOTE — Charles Babington covers politics for The Associated Press.

Copyright 2011 The Associated Press.