There was a Donald Trump-sized void in the Republican debate lineup tonight. The New York billionaire and Republican front-runner followed through on his boycott of the event, sponsored by Fox News, and held his own rally nearby.Without him there, the sparring was gentler and even, at times, friendly. Here’s a rundown of the most memorable exchanges:1. “The elephant not in the room”Fox moderator Megyn Kelly began the debate with the question hanging over the entire event: Trump’s absence. She asked Cruz what message his decision to skip the debate sends to Iowa voters. And Cruz didn’t disappoint in his response. “I will apologize to nobody for the vigorousness with which I will fight terrorism,” he said, adding, “You claim it is tough talk to discuss carpet bombing. It is not tough talk. It is a different fundamental military strategy than Barack Obama.”Cruz argued that “saturation bombing” was the tactic that helped the U.S. dominate the first Persian Gulf War.4. Arguing over the rulesChris Christie took a question about his comparison of Ted Cruz and Marco Rubio to Barack Obama, but he pivoted and instead delivered a lengthy critique of Hillary Clinton instead.Cruz attempted to jump in and respond, but moderator Chris Wallace cut him off, noting that Christie didn’t invoke his name during the response. Cruz protested, but Wallace wouldn’t relent.“I know you like to argue about the rules,” Wallace said, turning back to the debate.Later, Cruz grumbled that Wallace seemed to be goading the other candidates on stage to attack him. “It is a debate” Wallace responded. “There will be no progress on this issue in any way shape or form until you prove to the people of this country that illegal immigration is under control,” he said.8. “Washington bull”After Rubio and Cruz each accused the other of being politically malleable on immigration issues, Christie cut in.I feel like I need a Washington-English dictionary converter,” Christie said. “Ted can change his mind. Marco can change his mind. It’s perfectly legal in this country … “Stop the Washington bull and get things done.”Cruz bore the brunt of the attacks over immigration though with Rubio and Paul both slamming him for once supporting a pathway to legalization for the undocumented and now criticizing opponents for similar positions.“That’s an authenticity problem,” Paul said.Rubio picked up on the argument and hit Cruz even hard. “This is the lie Ted Cruz’s campaign is built on,” he said. “You’ve been willing to say or do anything to get votes. You worked for George Bush’s campaign. You helped design George W. Bush’s immigration policy … We’re not going to beat Hillary Clinton with someone who’s willing to say or do anything to win an election.”Cruz rejected the attacks as false.“John Adams famously said facts are stubborn things,” he said accusing Rubio of choosing to “stand with Barack Obama” on immigration. “We led the fight against amnesty.”9. Kasich defends Medicaid expansionThe policy was a pillar of Obamacare and Kasich was one of about a handful of Republican governors to embrace it (along with Christie). But he offered a full-throated defense of the decision, arguing that it brought in $14 billion from the federal government — “Our money,” he said — and used it to treat the mentally ill.“I don’t think they should live in prison or live under a bridge,” he said. “All I say is that when I study scripture, I know that people who live in the shadows should have a chance.”10. “A one horse country”Ben Carson got tongue-tied when asked how he’d handle a Vladimir Putin-backed incursion into Estonia. He didn’t directly answer the question, suggesting that the United States should do military exercises with all Baltic countries — Latvia, Lithuania and Estonia — and give Ukraine offensive weapons. The he went further. Then Cruz took an underhanded shot at the absent Trump. “If you guys ask one more mean question, I might have to leave the stage,” he joked.5. Muslim AmericansChris Christie argued that it’s possible to crack down on homegrown terrorism without profiling against Muslims, so long as people use common sense. Despite reports that neighbors of the San Bernardino killers hesitated to call police for fear of profiling Muslims, Christie said they should have called police — not because of their religion but because of suspicious activity.“Let law enforcement make those decisions,” he said. “It’s not for them to make those decisions about whether or not something is legal or illegal or profiling or not.”Ben Carson added that rising political correctness has been “dictating our policies” and “will kill us” if it isn’t checked.6. Kasich jabs Snyder on FlintJohn Kasich, one of just two sitting governors left in the GOP field, wasn’t exactly effusive with praise for fellow Republican Gov. Rick Snyder of MIchigan when asked about the unfolding water crisis in Flint, where lead and other chemicals have been found to be rampant in local tap water. “You’ve got to be on top of it right away,” he said when asked about Snyder’s handling of the episode.Kasich said he wasn’t sure about all the details of Snyder’s response, and he noted some officials had been fired or held accountable. But he said action should be quicker.“You realize that people are depending on you,” he said, adding, “When you see a problem you have to act quickly to be on top of it.”7. Bush vs. RubioOne of the sharpest exchanges came between Florida Sen. Marco Rubio and former Florida Gov. Jeb Bush over immigration, with Bush accusing Rubio of deciding to “cut and run” from an earlier position of a path to citizenship for undocumented immigrants.“That’s a tragedy,” he said.Rubio shot back that he moved away from his original position because he realized no consensus would ever emerge until the borders are protected. “I’m a maniac, and everyone else on this stage is stupid, fat, and ugly, and Ben,” — he gestured toward Ben Carson — “you’re a terrible surgeon,” he deadpanned. After a pause, he added, “Now that we’ve gotten the Donald Trump portion out of the way, I want to thank everyone here.”Cruz promised that Iowa wouldn’t just be flyover country but “fly-to country” if he’s elected president.2.The fight for the “liberty” voteSen. Rand Paul predicted that the libertarian vote that his father, Ron Paul, became associated with in his 2012 presidential run will remain in the “Paul household” in 2016, despite attempts by Cruz to poach it.“I don’t think they’re necessarily going to vote for Ted,” he said, pointing to Cruz’s absence from a debate on auditing the Federal Reserve, one of the hallmarks of the elder Paul’s movement.Cruz said he skipped the vote because he had a commitment in New Hampshire and knew the bill didn’t have the votes to pass. But he said he’d sign it as president. He also argued that he’s uniquely positioned to unite “disparate elements of the Reagan coalition” that includes libertarian voters.3. Cruz backs carpet bombingAsked about his call to “carpet bomb” ISIS into oblivion, Cruz stuck to his aggressive language. “Putin is a one-horse country, oil and energy,” he said.