Florida Gov. Ron DeSantis and former U.N. Ambassador Nikki Haley called each other liars and attacked each other’s leadership abilities Wednesday in their first one-on-one debate — and last opportunity to impress voters before Monday’s Iowa caucuses.

Each thinks they have the best chance to snatch the Republican nomination from former President Trump, who has a commanding lead in the polls and has refused to participate in the debates.

Monday’s caucuses kick off a series of nominating contests that will determine the GOP standard-bearer. New Hampshire holds its first-in-the-nation primary Jan. 23, Nevadans and South Carolinians vote next month, and Super Tuesday — when more than a dozen states, including California, hold caucuses or primaries — is less than eight weeks away. Despite facing 91 felony charges and attempting to overturn the 2020 election, Trump remains the front-runner in polling for the GOP nomination.

Haley and DeSantis clashed about foreign policy, entitlement changes and their respective gubernatorial records. But mostly they clashed over who was the bigger liar.

“She has a record, she makes statements,” DeSantis said about Haley, South Carolina’s former governor. “And I think part of the problem with her candidacy is now that she’s getting scrutiny: She’s got this problem with ballistic podiatry, shooting herself in the foot every other day.”

Haley repeatedly call DeSantis “desperate” and rolled her eyes when he attacked her. She also repeatedly called attention to the Florida governor’s high campaign spending and middling poll numbers.

“If you can’t manage a campaign, how are you going to manage a country?” she said, noting that DeSantis had spent more on private planes than on television ads. “If leadership is about getting things done, how did you blow through $150 million in your campaign and go down in the polls?”

Here are some key takeaways from the two-hour debate, which took place at Drake University in Des Moines and was broadcast on CNN:

Haley and DeSantis take on each other — and DeSantis bashes Newsom’s California

The debate was likely DeSantis and Haley’s last major opportunity to sway Republicans in the Hawkeye State before voters gather in subzero temperatures Monday to pick their nominee. New Jersey Gov. Chris Christie quit the race just a few hours before the debate began, allowing his supporters a chance to reassess his two former rivals.

The candidates kicked off the debate by repeatedly calling each other liars.

Haley unveiled a new campaign website that chronicled inaccurate statements she said DeSantis had made about her, a theme she continued Wednesday night.

“Every time he lies, Drake University, don’t turn this into a drinking game because you will be overserved by the end of the night,” she said.

DeSantis then compared Haley to California Gov. Gavin Newsom, whom he debated in November.

“I thought he lied a lot. Man, Nikki Haley may give him a run for his money, and she may even be more liberal than Gavin Newsom is,” DeSantis said.

DeSantis also attacked California’s policies during an exchange about immigration, saying the state gives free health insurance to any undocumented person who lives in the state. (The state expanded eligibility for its Medi-Cal program to any Californian — with or without papers — whose income is low enough to qualify.)

“We should not let states provide these benefits,” he said.

Although no single moment in the debate seems likely to substantially alter the course of the race, debates can buoy or sink candidacies. Haley’s recent surge is largely driven by strong debate performances. In a 2011 presidential debate, then-Texas Gov. Rick Perry’s campaign suffered after he failed to recall one of the three federal agencies he said he would eliminate.

But unless many of Trump’s current supporters change their preferences, he will be the GOP nominee.

Trump takes some hits for Jan. 6 and threats to suspend the Constitution

The candidates have spent much of the election avoiding direct hits on Trump’s character and his efforts to overturn the election, fearing they will alienate his loyal base of voters. But it’s made it harder for them to catch him in the polls.

Haley repeated her refrain that Trump was the right president for the right time, but took criticism of him a step further Wednesday, calling his attorney’s argument that he is immune from criminal prosecution “ridiculous,” and criticizing his false claims that he won the 2020 election rather than Joe Biden.

“He said that Jan. 6 was a beautiful day,” Haley said. “I think Jan. 6 was a terrible day. And we should never want to see that happen again.”

Despite those critiques, Haley has not ruled out serving as Trump’s running mate.

DeSantis was not quite as forceful but took issue with Trump’s call on social media recently to terminate the Constitution.

“You can’t just terminate the Constitution,” DeSantis said before adding that Trump is prone to “word-vomit from time to time on social media.”

But the crux of DeSantis’ argument was about Trump’s electability, asserting that a general election with Trump as the nominee would focus on Jan. 6 and Trump’s legal cases.

“Democrats and the media would love to run with that,” he said.

Once again, the elephant in the room was not in the room

At a town hall just two miles away at the Iowa Events Center, Trump batted away any suggestion that the two candidates would overcome him in the Iowa caucuses or New Hampshire primary. He told Fox News anchors Martha MacCallum and Bret Baier that in his first days in office, he would prioritize closing the border and drilling for oil.

“We have millions and millions of people here. It is not sustainable,” Trump said. “We are going to have the largest deportation effort in the history of our country. We’re bringing everybody back to where they came from. We have no choice.”

In response to a voter’s question if he would “protect all life,” Trump took credit for the abortion restrictions that swept across the country in the wake of the Supreme Court — with three Trump-appointed justices — overturning Roe vs. Wade.

“If it weren’t for me with Roe v. Wade, you wouldn’t be asking these questions,” he told her.

Trump also bragged about defeating Islamic State and said his tax cuts, which disproportionately benefited rich people and corporations, juiced the economy. He also rejected suggestions that he was to blame for a rise in political violence and said he’d be open to “mending fences” with former allies turned foes.

“Now I’ve gotten to know Washington, I’ve gotten to know the people,” he said. “I know the smart ones, the dumb ones, the weak ones, the strong ones.”

He repeated his refrain that the multiple criminal charges against him constitute “a witch hunt.”

Iowa: A winnower or a decider?

Iowans take deep pride in playing host to the nation’s first nominating contest. Haley recently drew their criticism by saying that although they go first in the nominating contests, New Hampshire “corrects” them and then “my sweet state of South Carolina brings it home.” She made the remarks at a town hall in New Hampshire, drawing laughter from the crowd.

Asked about the remark at an event and an interview in Iowa, she responded that she was joking. Not everyone is buying Haley’s explanation. Some in the crowd at the Des Moines town hall booed. DeSantis is airing television ads in Iowa attacking her over the flap.

“Iowans know when you’re telling a joke,” Haley said after DeSantis raised the quote in the first moments of the debate, before adding that the Florida governor’s campaign is largely confined to Iowa, not a winning strategy for winning the White House.

Haley is right that the candidate who wins Iowa does not always secure the party’s nomination. The last three GOP winners of competitive Iowa caucuses — Texas Sen. Ted Cruz, former Pennsylvania Sen. Rick Santorum and former Arkansas Gov Mike Huckabee — all failed in their efforts to be their party’s nominee. But then-Sen. Barack Obama’s victory in the 2008 Iowa caucuses was foundational to his successful campaign to beat front-runner Hillary Clinton for the Democratic nomination and ultimately win the White House.

Haley stands up for the establishment on Ukraine funding

Foreign policy is the area where Haley differs most from Trump. She argued Wednesday that continued funding for Ukraine is essential for protecting allies and preventing China from invading Taiwan. Opponents of helping Kyiv are misleading voters about the costs, which can be covered with cuts to Biden’s green agenda, she argued.

“This is about preventing war,” she said Wednesday. “This is about keeping our military men and women from having to fight a war, and you only do that when you focus on national security.”

DeSantis, a pro-Ukraine hawk when he served in Congress, has joined other Trumpist Republicans in repudiating aid, arguing that it’s too costly and Haley’s policy “is basically a carbon copy” of Biden’s.

“You can take the ambassador out of the United Nations, but you can’t take the United Nations out of the ambassador,” he said of Haley.

Mehta reported from Des Moines and Bierman from Washington. Times staff writer Faith E. Pinho in Los Angeles contributed to this report.