With Donald Trump refusing to debate, Sens. Ted Cruz and Marco Rubio sought to fire up support from Republican voters with tough words on immigration and terrorism Thursday while taking some shots at the front-runner.

Trump refused to participate in the Des Moines debate televised Thursday night by Fox News. He denounced moderator Megyn Kelly as being biased against him after her questions in the August debate about his past remarks about women. Instead, he held a fundraiser at the same time for wounded veterans at nearby Drake University.

The debate was a chance for his rival Republicans to build support before the Iowa caucus Monday. The candidates touched on a wide range of topics including the need for smaller government in Americans’ lives, the collection of telephone data on Americans in the fight against terrorists and how to wage a stronger war against ISIS.

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They had more time to do it without Trump, who has dominated the battle for attention throughout the campaign.

One of Trump’s favorite issues, illegal immigration, touched off fireworks. The Fox News moderators used video of past statements by Rubio and Cruz against them, showing both have altered their positions that once favored a pathway to legal status in Senate discussions a few years ago.

Rubio was pressed on his former openness to finding a way for immigrants in the country without proper documentation to eventually become citizens.

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“The quote was very specific, I said I don’t support blanket amnesty,” Rubio said of his past political campaign statements. “What I have always said is, this issue has to be solved.”

Former Florida Gov. Jeb Bush, a moderate on immigration, said he was “confused” by fellow Floridian Rubio’s flip-flop. He said immigration reform efforts died in Congress after Rubio “cut and run because it wasn’t popular with conservatives . . . he cut and run and that’s a tragedy.”

Bush said immigrants must have a path to “earn legal status . . . that is the conservative consensus, pragmatic path.”

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Cruz, who represents Texas, was confronted on his past support in the Senate for a compromise bill with Democratic President Barack Obama that would provide legalized status. He said he still opposes amnesty but supported the broad bill that had many elements he liked.

“We can build a fence, we can expand border patrols . . . what’s missing is the political will,” Cruz said. “We will end illegal immigration.”

“He can’t have it both ways,” responded Sen. Rand Paul of Kentucky. “It’s a falseness and that’s an authenticity problem.”

Then Rubio shifted into attack mode.

“This is the lie that Ted’s campaign is built on that he’s the most conservative guy,” Rubio said. “You will say anything to get votes . . . now you want to trump Trump on immigration.”

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New Jersey Gov. Chris Christie said the two senators’ explanations call for a “Washington-to-English dictionary converter” to understand what they really stood for. He said a candidate with executive experience, like himself, is needed.

“Stop the Washington bull and let’s get things done,” Christie said.

They also talked tough over how to deal with ISIS terrorists.

“I will hunt them down wherever they are and utterly and completely destroy ISIS,” said Cruz, Trump’s closest rival. He stood by his plan to “carpet bomb” ISIS.

“ISIS is the most dangerous jihadist group in the history of mankind,” said Rubio, who is gaining on Cruz in several polls. “That will take overwhelming military force . . . [but] you cannot destroy ISIS with a military that is being diminished,” he said.

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Paul parted with the other Republicans when he called for a strict limit on collecting phone call data on Americans broadly as a way to combat terrorists, including those who led a massacre in San Bernadino, California, last fall.

“I don’t think you have to give up your liberty for a false sense of security,” Paul said.

Ohio Gov. John Kasich sought a middle ground between the libertarian Paul and the more traditional conservatives on the stage, which could be critical for a Republican win in November.

“We have to come together as a country and we have to stop all the divisions,” Kasich said. “I have been assembling a team of people who want to join something bigger than themselves.”

Former neurosurgeon Ben Carson stressed his outsider role and closed with a surprise. He said to the Iowa audience, “Please think of our Founding Fathers as you listen,” then recited, word for word, the Constitution’s Preamble. “Folks, it’s not too late, enough said.”

The candidates also took their shots at Trump.

“I’m a maniac, and everyone on this stage is stupid, fat and ugly, and Ben you’re a terrible surgeon,” Cruz said in an opening quip. “Now that we’ve gotten the Donald Trump segment out of the way . . . ”

“It’s not about Donald Trump,” Rubio said. “He’s a great entertainer, the greatest show on Earth.”

“I kind of miss Donald Trump,” Bush said. “He was a little teddy bear to me . . . everyone else was in the witness protection program when I went after him.”