Former President Trump's two highest polling challengers chose to bring their fiercest attacks against him yet on the same day that former Gov. Chris Christie ended his anti-Trump campaign.

The big picture: The CNN debate in Des Moines, Iowa, stood out because the candidates repeatedly hit Republican presidential frontrunner Trump rather than just attacking each other, as has been the case in most of the previous debates.

• After a first hour where former UN Ambassador Nikki Haley and Florida Gov. Ron DeSantis repeatedly accused the other of lying and hurled constant attacks at each other, the two spent much of the second hour going after Trump.

Zoom in: Both candidates agreed that Trump, who snubbed the debate and instead sat for a Fox News town hall, should have been on stage on Wednesday night.

• "Don't ask me what President Trump thinks. You need to have him on this debate stage and ask him for yourself," Haley said.
• DeSantis said Trump should have joined them onstage to answer tough questions, such as "why he wants to build a $1 billion-plus, big, beautiful new FBI building right in the heart of the swamp in Washington, D.C."
• "[H]e owes it to you here in Iowa to explain this change he's had in his positioning," DeSantis said of Trump's views on abortion.

State of play: Haley has been increasingly critical of Trump in the past several weeks, and on Wednesday she hit the former president on his conduct on Jan. 6, China, electability and more.

• "I think what happened on January 6 was a terrible day. And I think President Trump will have to answer for it," Haley said.
• "We don't need this chaos anymore," she said of Trump, adding that she would "make America proud again" — a tweak of the former president's slogan.
• The former South Carolina governor also mocked suggestions by Trump's lawyers at his Tuesday appeal hearing in D.C. on his immunity claims that a president could order SEAL Team Six to assassinate a political rival and be immune from criminal prosecution unless he's impeached and convicted by Congress.
• "That's absolutely ridiculous," Haley said. "We need to use some common sense here. You can't go and kill a political rival and then claim immunity from a president," she said.

Meanwhile, DeSantis was more selective during the two-hour debate in attacking Trump, and pivoted away from questions about his conduct on Jan. 6.

• "I think it's fine to criticize Donald Trump, and I know the media brings this up a lot. But you know who else deserves to be criticized? The people that violated the Constitution during COVID," he said.
• DeSantis instead made an electability argument against Trump. "If Trump is the nominee, it's going to be about January 6, legal issues, criminal trials," he said. "The Democrats and the media would love to run with that."

Yes, but: DeSantis slammed Trump over unfinished promises he made while president.

• "He said he was going to build a wall and have Mexico pay for it, he did not deliver that. He said he was going to drain the swamp, he did not deliver that," DeSantis said.
• The Florida governor also criticized Trump's handling of the protests in 2020 after the murder of George Floyd.
• "He was president during the worst rioting in the modern history of this country," DeSantis said of Trump. "He sat in the White House and tweeted 'law and order,' but he did nothing to ensure law and order. As your president, I will never let our cities burn."

Of note: The two candidates still jabbed at each other — with Haley showing up with a new campaign website, desantislies.com, hitting DeSantis over his record.

• DeSantis called Haley "another mealy-mouthed politician who just tells you what she thinks you want to hear," while Haley repeatedly directed viewers to her new campaign website.
• "You just can't trust what he says," Haley said after DeSantis answered a question about his economic platform, later calling the Florida governor "desperate."

The bottom line: While the two presidential hopefuls clashed on stage at Drake University in Des Moines, Trump was met with a friendlier crowd during his event two miles away.

Go deeper: Christie caught on hot mic saying Haley is going to get "smoked"