DES MOINES, Iowa (CBSNewYork/CBS News/AP) — Heated exchanges erupted among the Republican presidential candidates Thursday night in Des Moines, Iowa in their final debate before the Iowa caucuses — all without front-runner Donald Trump.

As the debate began, Trump’s chief rival U.S. Sen. Ted Cruz (R-Texas) was asked at the very start of the debate about Trump’s absence. He offered a mocking, tongue-in-cheek remark, as CBS2 Political Reporter Marcia Kramer reported.

“Let’s say I’m a maniac, and everyone on this stage is stupid, fat and ugly, and Ben (Carson), you’re a terrible surgeon — now that we’ve gotten the Donald Trump portion out of the way,” Cruz said.

U.S. Sen. Marco Rubio (R-Florida) said the focus should not be on Trump, but about undoing the perceived damage done by President Barack Obama.

“It’s not about Donald Trump. He’s an entertaining guy. He’s the greatest show on earth. This campaign is about the greatest country in the world,” Rubio said.

The candidates soon moved on from discussing Trump, focusing on the subjects of where conservatives have been this year. U.S. Sen. Rand Paul (R-Ky.) took issue with other Republicans who had favored the bulk collection of data by the National Security Administration – saying it had not prevented any terrorist attacks.

Meanwhile, Rubio reiterated an earlier statement that he would go after terrorists and have them questioned on everything they know at the Guantanamo Bay detention center.

Other candidates also set their sights on the Democrats and frontrunner Hillary Clinton rather than Trump – among them New Jersey Gov. Chris Christie.

Christie was asked whether Cruz and Rubio’s records on national security made the country less safe and whether they were qualified to be president, but he talked about Clinton instead. He talked about when she was asked about her email use at a Democratic town hall earlier this week, as CBS News reported.

“She did it for convenience, for her convenience,” Christie said. “She put America’s secrets at risk for her convenience. She put American intelligence officers at risk for her convenience…let me tell you who’s not qualified to be president of the United States, Chris. Hillary Rodham Clinton did that to our country she is not qualified to be president of the United States.”

Christie was also asked to name something he would cut entirely from the federal budget.

“How about one I’ve done in New Jersey for the last six years, and that’s get rid of Planned Parenthood funding,” he said.

Asked for something bigger than that, he said, “When you see thousands upon thousands upon thousands of children murdered in the womb, I can’t think of anything bigger than that.”

The moderators also launched tough lines of questioning at Cruz. They asked whether his record matched his rhetoric on fighting ISIS.

He has promised to carpet bomb the group, but did not support President Obama’s request for military action to enforce his red line in Syria, and has not voted for the defense authorization bill the last three times it was on the floor.

Cruz said his promises are “not tough talk” but rather a “different fundamental military strategy” than Mr. Obama has put forward.

Cruz went on to complain about the questions moderators were asking, saying several questions had invited his opponents to attack him.

“If you guys ask one more mean question, I might have to leave the stage,” he said.

Rubio in turn said he promised not to leave the stage “no matter what you ask me.”

Rubio was later asked about his support of legislation calling for a path to citizenship for undocumented immigrants, when he had come out against “blanket amnesty” while running for the U.S. Senate.

Rubio said he had not reversed his position in any way, and the point was that the issue of undocumented immigration has not been dealt with.

“They’ve been talking about this issue for 30 years and nothing ever happens,” Cruz said.

Rubio said if he were elected president, he would focus on keeping ISIS out and enforcing immigration laws.

A debate later erupted between Cruz and Rubio about immigration, with both accusing the other of flip-flopping on his position.

The exchange was spurred by video clips of past statements Ted Cruz has made about immigration led to a heated exchange.

The clips showed Cruz claiming he would support immigration reform legislation if some of his amendments had been approved. But at the debate, Cruz said his intention was to ensure people in the country illegally couldn’t gain legal status.

Paul responded that Cruz claims that only he is “perfect” on immigration issues.

Marco Rubio jumped into the exchange, calling Cruz’s comment about his superiority on immigration “the lie that Ted’s campaign is built upon.”

Cruz accused Trump of taking a 180-degree turn on immigration, saying while running for U.S. Senate, “On the issue of people here illegally, we can reach compromises.”

“Now you want to trump Trump on immigration,” Rubio said. Trump has called for the removal of all people in the country illegally.

Meanwhile, Cruz said Rubio had taken a stance against amnesty while running, but had now gone back on it.

“When we came to Washington, (Rubio) made a different choice” and went with donors who supported some form of amnesty, Cruz said.

Christie stepped in and dismissed both Cruz and Rubio as suffering from Washington myopia.

“I feel like I need a Washington English dictionary converter,” he said.

Christie said Cruz and Rubio were both welcome to change their minds on positions, but they had to own up to it.

“When you’re a governor, you have to admit it. You can’t hide behind parliamentary tricks. That’s the difference,” he said. “That’s the kind of leader we need in the White House. Stop the Washington bull and let’s get things done.”

Neurosurgeon Ben Carson also called for a hardline immigration policy, saying even though most immigrants are likely not dangerous, precautions must be taken if even one in 10 people in a hypothetical group of people coming to someone’s house might be terrorists.

The need for a greater ability for military engagement was also a major theme throughout the debate. Both Rubio and former Florida Gov. Jeb Bush said the U.S. rules of engagement are hampering the military unnecessarily and preventing them from successfully taking on U.S. enemies abroad, CBS News reported.

For Trump’s part, he refused to back off his decision to boycott Thursday’s prime-time faceoff.

His campaign insisted that debate host Fox News crossed a line with a sarcastic statement mocking him and continued to criticize moderator Megyn Kelly. In turn, Fox accused Trump’s camp of trying to terrorize its employees.

“They think they can toy with Mr. Trump,” campaign manager Corey Lewandowski said Wednesday on MSNBC’s “Morning Joe.” “Mr. Trump doesn’t play games.”

Trump reiterated his plans to skip the debate in an interview Wednesday on Fox News, saying, “I just don’t like being used.”

There was little sense that Trump’s move would significantly change the trajectory of the Republican contest in Iowa. While the former reality television star holds a big lead in most national polls, he and Cruz are locked in a tight race here.

“My sense is those Iowa Republicans who weren’t fans of Donald Trump before yesterday, this has only validated their opinion of him, and those Iowans who have been drawn to his passionate attack on the media and political elites in our country are even more emboldened by their guy today,” said former Iowa GOP chairman Matt Strawn.

Thirty-eight percent of Iowans said in a poll that they could change their mind about who to vote for ahead of the caucus.

A recent CBS News/New York Times poll shows Trump leading nationally among his GOP opponents with 36 percent of support from Republican primary voters. Cruz is second at 19 percent.

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