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(CNN) -- Wednesday night's explosive fourth Republican presidential debate made clear why former President Donald Trump has so far skipped the 2024 primary debate circuit.

The four contenders on stage — former South Carolina Gov. Nikki Haley, Florida Gov. Ron DeSantis, former New Jersey Gov. Chris Christie and businessman Vivek Ramaswamy — spent most of the two-hour debate slamming each other.

Amid the smallest field of debate yet and facing mounting pressure with Iowa's caucuses less than six weeks away, candidates were able to showcase their political beliefs and explore important differences. There were also a number of memorable personal photographs.

Ramaswamy referred to Haley as "Dick Cheney lipstick." Christie poked fun at Ramaswamy's "know-it-all mouth." DeSantis said Haley "sinks every time the left goes after her."

"I love the attention, guys. Thank you for that," Haley replied.

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What their showdown in Alabama, presented by NewsNation, made clear is that all of the candidates on stage believe they should first be seen as the GOP's only alternative to the former president before making a more specific case against him.

But he also underscored why Trump hasn't paid a price in the polls for skipping debates. There were attacks on the former president: Christie, whose campaign is based on an anti-Trump message, made sustained arguments against his return to power, while Haley criticized his approach to China and DeSantis said Trump had failed to deliver on his promise to "drain the swamp" and make Mexico pay for a border wall. But those moments were exceptions in a debate dominated by clashes between the candidates who were actually present.

Here are five takeaways from the fourth debate of the Republican primary.

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From left to right, Republican presidential candidates Chris Christie, Nikki Haley, Ron DeSantis and Vivek Ramaswamy participate in the fourth primary debate in Tuscaloosa, Alabama, on Dec. 6, 2023. (PHOTO: Justin Sullivan/Getty Images North America/Getty Images)

DeSantis and Ramaswamy versus Haley

Is this the clearest sign of Haley's rise in the race? Her opponents thrust her into the spotlight for much of the first hour of the debate.

DeSantis waited 30 seconds after his first response before taking aim at Haley, pushing her into a dispute over which bathrooms transgender people should be able to use. And in his first response, Ramaswamy picked up where he left off in the third debate, taking aim at Haley for her time on the board of directors of Boeing, a company that has a major manufacturing facility in the state she once ruled.

At several points, DeSantis and Ramaswamy teamed up to rack up criticism, focusing on the support she's received lately from donors like LinkedIn co-founder Reid Hoffman, a Democratic donor who sent $250,000 to a super PAC that supports her, and interest in people like BlackRock CEO Larry Fink.

Later in the debate, Ramaswamy held up his notebook on which he had written "Nikki = Corrupt."

Haley, who also recently received endorsements from the conservative group Americans for Prosperity, said she welcomed help wherever it came from, but wouldn't let it dictate her policies. And he said his competitors would also accept the money if offered. DeSantis' political operation had pushed for support from American for Prosperity and has seen an exodus of wealthy corporate donors who backed him in the past.

"They're just jealous," Haley said. "They wish they were being supported."

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For DeSantis, the focus on Haley was particularly notable because before past debates, his campaign suggested that his position in the polls (among non-Trump candidates) would make him a lightning rod for attacks. However, he made it a point to attack Haley early on and frequently as he tries to fend off the growing threat of his campaign in early states like Iowa.

DeSantis stepped in after her China response to improve her track record of working with Chinese companies as governor of South Carolina. Haley responded that DeSantis has done the same in her state.

"I have a history of standing up for myself and doing the right thing," DeSantis said.

To which Haley responded, "You have a history of lying."

Christie was the exception on stage, coming to Haley's defense as Ramaswamy hurled insults aimed at her foreign policy skills.

"We disagree on some issues and we disagree on who should be president of the United States, but we don't disagree on this — this is a smart, successful woman," Christie said.

Haley turned to him and articulated, "Thank you."

Christie gets her groove back

For months, Christie has struggled to recreate the magic of the 2016 presidential primary debate season, when he criticized Florida Sen. Marco Rubio for repeating a phrase from the debate. Although Christie didn't get very far in that primary, Rubio struggled to overcome the perception that he was a robot.

In Tuscaloosa, the former New Jersey governor tapped into some of that energy, portraying his opponents as immature, annoying and unfit for the job. It may not help him win the nomination, but it's also not making it any easier for the rest of the candidates, particularly DeSantis and Ramaswamy.

Christie tried to portray DeSantis as someone who wasn't willing to answer basic questions. When DeSantis was asked whether, as president, he would send U.S. troops to Gaza to rescue American hostages held by Hamas, Christie weighed in.

"When you're president of the United States, you won't have a choice whether or not to answer that question," he said.

Later in the debate, DeSantis was asked if he thought Trump was fit for office. He responded by saying that "Father Time is undefeated." Christie struck again.

"Either you're scared or you're not listening. It's a simple question to answer," Christie said. "I'm a simple guy. I listen to the question and answer it."

With Ramaswamy, Christie continued his tendency to backtrack on comments. During a tug-of-war in which Christie criticized the Ohio businessman's proposal for a peace deal between Ukraine and Russia, the former New Jersey governor accused Ramaswamy of denying what he had said during the election campaign when he was on the debate stage, and of being irritating.

"This is the fourth debate where they would vote for you, in the first 20 minutes, as America's most obnoxious braggart," Christie said.

But a lot has changed since the 2016 election cycle, including Christie's loyalty to Trump. He saved some of his most solemn criticism for his three opponents, who, he said, were afraid of "offending" the former president.

"You have to be willing to offend with the truth," he said.

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"The One Who Should Not Be Named"

After watching his three rivals battle it out for the first 17 minutes of the debate, Christie tried to reframe the debate with a reminder: Trump is vastly outpacing all of them in the polls.

"I've got these three guys who seem to be competing with Voldemort: 'The one who shouldn't be named,'" the former New Jersey governor said, referring to the Harry Potter villain whose name the characters avoided saying. "They don't want to talk about it."

Christie suggested that other candidates are avoiding directly confronting Trump because they don't want to limit their own chances of becoming his vice presidential nominee, or their presidential prospects for 2028.

"When you go and tell the truth about someone who is a dictator, a bully, who has shot everyone (whether they've done him great service or not over time) and who dares to disagree with him, then I understand why these three are shy about saying anything about it," Christie said. "Maybe it's because they have aspirations for the future; Maybe those future aspirations will be now or maybe four years from now. But the crux of the matter is that the truth needs to be told."

Perhaps the most telling thing about the state of the GOP primary was the reaction to Christie's comments.

Questions posed to his rivals in the opening moments of the debate had provoked fierce, and sometimes personal, back-and-forth exchanges. Christie's comments, however, were met with silence by his rivals.

Later in the debate, others offered limited criticism of Trump. Haley argued that the former president had not been tough enough against China. DeSantis said Trump had failed to deliver on his 2016 campaign promise to make Mexico pay for a wall on the U.S. southern border.

But only Christie made a sustained case against the former president, a theme he returned to in his final speech, when he said Trump would not be allowed to vote in the 2024 election because "before that date he will be convicted of felonies."

When his comments were met with boos, Christie said, "They can boo all they want and still deny reality. But if we deny reality as a party, we'll have four more years of Joe Biden."

The Culture Wars Are Coming

DeSantis' "war on awakening" took a back seat during the first three GOP debates, which focused more on foreign policy, eligibility, U.S. border policy and the economy.

This time, however, he used two domestic culture war issues — environmental, social, and governance, or ESG, investment, and transgender rights — to aid in his efforts to portray Haley as a moderate.

In his first response, DeSantis went from a question about his campaign to criticizing Haley for gender-affirming attention to transgender minors.

"I did a bill in Florida to stop the gender mutilation of minors," DeSantis said. "She opposes that bill. She thinks it's OK and the law shouldn't get involved in that."

His comments reflected the points made in a video that Never Back Down, the super PAC backing DeSantis, released ahead of the debate. The ad accused Haley of being unwilling to "fight the left's agenda."

Haley said "the law should be kept out of it" during a June interview with CBS News. But he added that parents should take the lead and did not endorse gender transition for young people.

"This is a job that needs to be handled by parents, and then when the child turns 18, if they want to make a more permanent change, they can do it," she said.

DeSantis later joined Ramaswamy in tying Haley's support from wealthy donors to the ESG investment movement Wednesday night.

"They want to use economic power to impose a leftist agenda on this country," he said.

Ramaswamy Unleashes a Number of Conspiracy Theories

In what could be his last appearance on the stage of a Republican presidential debate, Ramaswamy gave the clearest voice yet to the extreme conspiratorial wing of the Republican Party.

He unleashed a series of false and provocative conspiracy theories, touting himself as the only candidate in the race willing to accept them.

Among those theories: Ramaswamy called the Jan. 6, 2021, attack on the U.S. Capitol by Trump supporters "an inside job." He said the 2020 election was "stolen by Big Tech." He said the government "lied to us for 20 years" about Saudi Arabia's involvement in the Sept. 11 attacks.

And he said the "great replacement" theory — a racist conspiracy theory that suggests non-white people are being brought into Western countries to replace white voters and achieve a political agenda — "is not a big right-wing conspiracy theory, but a basic statement of the Democratic Party platform."

He also said that the biggest threat to the United States is "the deep state that at least Donald Trump tried to confront."

Ramaswamy later used his closing statement to claim that the "climate change agenda is a hoax."

"If you thought covid was bad, what comes with this climate agenda is much worse. We should not kneel before this new religion," he said. "That's what it is. It is a substitute for a modern religion. We are flagellating ourselves and losing our modern way of life by bowing down to this new weather god, and that will end under my watch."

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