Factbox: Key quotes from Republican presidential debate

Republican presidential candidates (L to R) U.S. Rep. Ron Paul, former U.S. Senator Rick Santorum, former Massachusetts Governor Mitt Romney and former Speaker of the House Newt Gingrich listen to moderator John King (R) during the Republican presidential debate in Mesa, Arizona, February 22, 2012.

(Reuters) - Republican presidential contenders competing to challenge President Barack Obama faced off on Wednesday in Arizona, where one of the next nominating contests takes place on February 28.

Here are some of their main quotes:

MITT ROMNEY, FORMER MASSACHUSETTS GOVERNOR

Attacking rival Rick Santorum:

"Let's not forget that four years ago, you not only endorsed me ... and said and this is the guy who is really conservative and we can trust him. Let's not forget you said that ..."

Criticizing Santorum on earmarks, which is funding set aside often for local projects:

"While I was fighting to save the Olympics, you were fighting to save the "Bridge to Nowhere."

On Obama's contraception mandate:

"I don't think we've seen in the history of this country the kind of attack on religious conscience, religious freedom, religious tolerance that we've seen under Barack Obama."

On the threat of a nuclear Iran:

"This is a president who should have instead communicated to Iran that we are prepared, that we are considering military options. They're not just on the table. They are in our hand."

RICK SANTORUM, FORMER U.S. SENATOR FROM PENNSYLVANIA

Attacking Romney for his criticism of earmarks:

"You're entitled to your opinions, Mitt. You're not entitled to misrepresent the facts, and you're misrepresenting the facts. You don't know what you're taking about."

On calling contraceptives "dangerous":

"What we're seeing is a problem in our culture with respect to children being raised by children, children being raised out of wedlock."

On voting for Title X, a federal program that provides access to contraceptives:

"I admit I voted for large appropriation bills and there were things in there I didn't like, things in there I did, but when it came to this issue, I proactively stepped forward and said that we need to do something at least to counterbalance it."

"While I have a personal...objection to it; even though I don't support it ... I voted for bills that included it and I made it very clear in subsequent interviews that I don't support that."

Attacking Romney:

"Yes governor, you balanced the budget for four years. You have a constitutional requirement to balance the budget for four years. No great shakes ... don't go around bragging about something you have to do."

NEWT GINGRICH, FORMER SPEAKER OF THE HOUSE OF

REPRESENTATIVES

On reducing the federal deficit:

"Everybody talks about managing the current government. The current government is a disaster."

On immigration:

"It is utterly stupid to say that the United States government can't control the border. It's a failure of will, it's a failure of enforcement."

On birth control and the media:

"I just want to point out ... in the 2008 campaign, not once did anybody in the elite media ask why Barack Obama voted in favor of legalizing infanticide."

Describing himself in one word:

"Cheerful"

RON PAUL, U.S. REPRESENTATIVE FROM TEXAS

On Santorum:

CNN moderator John King: "Congressman Paul, you've questioned the fiscal conservative credentials of all these gentlemen but particularly this week Senator Santorum. You have a new television ad that labels him a fake. Why?"

Paul: "Because he's a fake."

"This idea of being fiscally conservative now that we're running for office and we're going to repeal something that we did before, I mean, this, it loses credibility."

On birth control:

"I think it's sort of like the argument ... Guns don't kill, criminals kill ... The pill is there ... but the pills can't be blamed for the immorality of our society."

(Reporting By Lily Kuo)