DES MOINES, Iowa — Nikki Haley and Ron DeSantis called each other liars and insulted each other's records and character in the opening minutes of Wednesday's Republican primary debate, underscoring the high stakes for each of them with less than a week before the Iowa caucuses.

“We don’t need another mealy-mouthed politician who just tells you what she thinks you want to hear, just to try to get your vote and then to get in office and to do her donors’ bidding,” DeSantis said in an early barb.

“He’s upset that his campaign is exploding,” Haley said in her reply.

The former U.N. ambassador directed viewers to a website her campaign created chronicling what she said were DeSantis' lies. The Florida governor in turn tried to send people to his website, where he said he collected “all the greatest hits” of Haley's false statements.

Standing at lecterns an arm's length apart, DeSantis and Haley both sought a strong debate performance in Iowa without their lower-polling rivals by their side to lift their campaigns in the final days before Monday’s caucuses, where a good showing could provide much-needed momentum as they try to become the primary alternative to Donald Trump.

The former president and GOP front-runner skipped the CNN debate in Des Moines to appear in a Fox News town hall in the same city.

Neither Haley nor DeSantis answered directly a question about whether Trump “has the character to be president.”

“His way is not my way,” Haley said. “I don’t have vengeance. I don’t have vendettas. I don’t take things personally.”

DeSantis said Trump failed to deliver on his promises to build a border wall and make Mexico pay for it, prosecute Hillary Clinton, “drain the swamp” or eliminate the national debt.

“We need to deliver and get this stuff done,” DeSantis said.

Hours before Haley and DeSantis took the stage, New Jersey Gov. Chris Christie announced he was dropping out of the race, a curveball with major implications. Christie, by far the most aggressive Trump critic running for the GOP nomination, had faced intense pressure to step aside so opponents of the former president could unify behind a single candidate and improve the odds of dethroning the front-runner.

Christie, along with biotech entrepreneur Vivek Ramaswamy, did not qualify for Wednesday’s debate after appearing in earlier events.

Trump said he’s “not exactly worried” about Christie dropping out. He said he agreed with comments Christie made on a hot mic ahead of his announcement, when he said Haley is “going to get smoked” and is “not up to this.”

Wednesday's debate is especially important for Haley, a politician long known for her disciplined approach to messaging. That reputation has been tested recently after a series of gaffes, including her failure to mention slavery as the root cause of the Civil War and a quip that New Hampshire voters will have a chance to “correct” the results that emerge from Iowa.

The debate offers Haley a chance to reset a campaign that has come under fresh scrutiny by everyone from her GOP rivals to President Joe Biden, a sign that her opponents in both parties see her as a rising contender. While she is likely to pay more attention to Trump as her allies argue she’s the only person equipped to beat him, DeSantis is expected to train his focus on Haley.

“Now she's in a situation where she's getting scrutiny, and it's almost like every day she answers questions, something happens where she's putting her foot in her mouth,” DeSantis told reporters Tuesday after appearing on a Fox News Channel town hall.

After several debates filled with candidates who likely have minimal chances to win the nomination, many expected caucusgoers said they planned to pay close attention to a debate featuring Trump’s main opponents.

Some of Haley’s strongest moments have come during the previous four debates, as she has sparred with her onstage rivals.

A CNN/UNH poll conducted in New Hampshire this week suggested that Haley could be approaching Trump’s top spot in the state. About 4 in 10 likely Republican primary voters in New Hampshire chose Trump, while about one-third picked Haley.

While for months she’s taken questions at many of her campaign events, styled as town halls during which she entertains questions from the gathered crowd, Haley has rarely spoken with the reporters covering her events, held news conferences or sat for print interviews. She did not speak to reporters after her own Fox News town hall on Monday, a day before DeSantis' appearance.

Haley would say a day after her original Civil War comment that “of course” slavery was a root cause. But she has been asked repeatedly about the remark, lending more fodder to her opponents.

DeSantis has been quick to try to turn some of Haley’s words against her. He's repeatedly brought up her comment that New Hampshire would “correct” Iowa's results — something that Haley later said was a joke about the rivalry between the two early-voting states.

Trump has also ramped up his attacks of Haley as she gets more attention. In recent weeks, his campaign has accused her of not being conservative enough on immigration and for proposing, while serving as South Carolina’s governor, to raise the state’s gas tax as part of a broader budget package that ultimately wasn’t adopted.