DES MOINES, Iowa (CNN) -- Ted Cruz opened the final Republican presidential debate before the Iowa caucuses Thursday by answering a question from Fox News moderators about "the elephant not in the room" -- Donald Trump.
"Let me say, I'm a maniac," the Texas senator said in response to Megyn Kelly, channeling Trump's barbs. "And everyone on this stage is stupid, fat and ugly and Ben, you're a terrible surgeon. Now that we've gotten the Donald Trump portion out of the way..."
Marco Rubio said the 2016 presidential campaign is "not about Donald Trump."
"He's an entertaining guy, he's the greatest show on earth," the Florida senator said, adding that the focus should be on preventing Hillary Clinton from getting to the White House.
Jeb Bush, who has been increasingly combative with Trump during the debates, joked that he wished Trump was there. He also appeared to take a swipe at his rivals on stage for not taking on Trump as aggressively as he has.
"I kind of miss Donald Trump. He was a little teddy bear to me," Bush said. "Everybody else was in the witness protection program when I went after him."
Trump, the GOP presidential front-runner, threw an unexpected curveball into the 2016 campaign this week when he declared that he would boycott the debate amid an escalating feud with Fox News. As seven of his rivals stepped onto the debate stage, Trump supporters were gathered less than three miles away at Drake University, where the billionaire businessman was hosting a rival event billed as benefiting veterans.
In an interview with CNN's Brianna Keilar on Thursday, Trump said Fox News "apologized" to him for a mocking statement the television network issued two days before the GOP debate.
Trump said that while the network "could not have been nicer" as it tried to woo him back into attending the debate, he would stick to his plan of holding the event for veterans.
"I was treated very unfairly by Fox. Since then they've been excellent, they've been very nice, but it's too late," he said in the interview aboard Trump's private plane.
Trump likened his decision to skip the debate to how he would lead the country as president of the United States.
"I wanted to fight for myself just like I'll fight for the country," Trump said. "You have to stick up for yourself, you have to fight for yourself and you have to fight for your country."
A Fox News spokesperson said Roger Ailes, the network's chief executive, had "three brief conversations" with Trump on Thursday.
"In the course of those conversations, we acknowledged his concerns about a satirical observation we made in order to quell the attacks on Megyn Kelly, and prevent her from being smeared any further," the spokesperson said. "Furthermore, Trump offered to appear at the debate upon the condition that FOX News contribute $5 million to his charities. We explained that was not possible and we could not engage in a quid pro quo, nor could any money change hands for any reason."
The spokesperson went on: "In the last 48 hours, we've kept two issues at the forefront --- we would never compromise our journalistic standards and we would always stand by our journalist, Megyn Kelly. We have accomplished those two goals and we are pleased with the outcome. We're very proud to have her on stage as a debate moderator alongside Bret Baier & Chris Wallace."
Debating without Trump
Thursday marked the first time that Trump's rivals found out what it's like to debate without his bluster and theatrics dominating the stage. The stakes were highest for Cruz, Trump's closest rival here in the Hawkeye State. The interaction between the two men, who have spent the last week slinging a flurry of political attacks at one another, were among the most highly anticipated dynamics in the debate as they are battling to finish first in Iowa on Monday.
Flanking Cruz on stage were six other top candidates: Rubio, Bush, Ben Carson, Chris Christie, John Kasich and Rand Paul. Trump's absence in the debate will force each of these candidates to varying degrees to recalibrate their debate night strategies.
Trump was even a presence at an earlier undercard debate featuring four lower-polling candidates -- Carly Fiorina, Mike Huckabee, Rick Santorum and Jim Gilmore. Santorum quickly expressed deep frustration with the drama surrounding Trump's decision to skip the debate.
"The entire lead-up to this debate was about whether Donald Trump was going to show up to the next debate," Santorum said. "The people of Iowa ... care a lot about the issues. They care about who's going to be the leader of the free world."
Santorum and Huckabee, two previous winners of the Iowa caucuses, plan to attend Trump's veterans event after the debate.
Gilmore, who has not qualified for most undercard debates, mocked Trump's rival event, as he called himself "the only veteran" running for president this cycle.
"I'm not going to any Donald Trump event over across town on some sort of faux veteran sort of issue," Gilmore said.
He appeared to relish his time in the spotlight, taking issue on several occasions with how many questions he was being asked by the moderators.
"Did you miss me? Did you skip me?" Gilmore blurted out when a question went to Huckabee.