Gov. Jeb Bush (Fla.): "If you (Donald Trump) think this [debate] is tough and you're being treated unfairly, what do you think it's gonna be like dealing with Putin? This is a tough business."

Donald Trump: "Oh, I know, you're a tough guy Jeb. I know."

Bush: "You're never going to be president of the United States by insulting your way to the presidency."

Trump: "Well, let's see. I'm at 42 and you're at 3 [percent in the polls], so so far I'm doing better. You started over here [next to me on the stage] and you're moving over further and further. Soon you're gonna be off the end."

The heated exchange above was just one of many throughout Tuesday night's Republican presidential debate. From immigration to data collection to the Middle East, presidential hopefuls ardently expressed their opinions on a host of issues.

Several of the most prominent moments in the debate emerged as Bush, Ted Cruz (R-Texas), Rand Paul (R-Ky.), Marco Rubio (R-Fla.) and Trump spoke out against one another.

Government surveillance

During the early stages of the debate, CNN moderator Wolf Blitzer asked Rubio to express why he felt the federal government should have access to phone records. He then explained how "the metadata program was a valuable tool that we no longer have."

Paul immediately challenged Rubio by arguing large-scale data collection unnecessarily invades Americans' privacy.

"I think Marco gets it completely wrong," Paul said. "We are not any safer through the bulk collection of all Americans' records. In fact, I think we're less safe. We get so distracted by all the information."


Shortly after, Paul and Rubio had an intense back-and-forth about immigration.

While Rubio urged for a reformation of the legal immigration system and said there is no trust in enforcement of the federal law, he supported a path to citizenship for undocumented immigrants; ultimately leading to further criticism.

"He is the weakest of all the candidates on immigration," Paul said. "He is the one for an open border that is leaving us defenseless. If we want to defend the country, we have to defend against those who are coming in and Marco has more of an allegiance to Chuck Schumer and the liberals than he does to conservative policy."

Cruz also chimed in by criticizing Rubio's immigration plans for granting amnesty and resulting in a less secure border.

But the most memorable moments of the debate occurred between Trump and Bush.

Middle East

When asked how intentionally killing innocent civilians would set America apart from ISIS, Trump said he would justify attacking families. Instantaneously, Bush argued Trump's response to attack families was not a serious solution.

Trump countered by arguing Bush was weak on ISIS.

"He's a very nice person, but we need toughness," Trump said. "We need intelligence and we need toughness."

Bush argued Trump was using his usual bullying antics to attract support

"Donald, you're not gonna be able to insult your way to the presidency," Bush said. "Leadership is not about attacking people."

While Bush, Cruz, Paul, Rubio and Trump generated much of the focus of the debate, other important discussions took place.

Other candidates have standout moments

Ben Carson entered the debate having received much criticism for being unaware of foreign affairs. But as the debate progressed, he proved himself to be knowledgeable about global issues.

During a discussion on air strikes in Syria and overthrowing President Bashar al-Assad, Carson put the conflict in a historical context.

"The Middle East has been in turmoil for thousands of years," Carson said. "For us to think that we're gonna go in there and fix that with a couple little bombs and a few declarations is relatively foolish."

Christie also gave a decent performance when articulating how he would be tough with Russia.

Christie said he would threaten Putin if he entered the no-fly zone and would not be a "weakling" like Hillary Clinton or President Barack Obama.

Carly Fiorina and Gov. John Kasich (Ohio) had few shining moments in the debate as they seldom jumped into conversations. But while other candidates began arguing with one another, Fiorina and Kasich stepped in to express how such arguments exemplify Americans' frustration with politicians.

At one point during the debate, Fiorina quoted former British prime minister Margaret Thatcher.

"If you want something talked about, ask a man," Fiorina said. "If you want something done, ask a woman."

In Kasich's opening statement he said his daughter doesn't enjoy politics because of the deep division it causes. Throughout the debate, he readdressed the importance of creating a more unified country.

Surprising moment of unity

Although most of the candidates seized advantage of opportunities, to differentiate from their competitors, Trump and Cruz refused to attack one another.

When Trump was asked about an event when he previously criticized Cruz's temperament, Trump refused to engage in an attack.

"Cruz has a wonderful temperament," Trump said. "He's just fine. Don't worry about it."

Cruz then refused to attack Trump.

"All nine of the people here would make an infinitely better commander-in-chief than Hillary Clinton," Cruz said.

Moving forward

While nine candidates appeared in the main debate Tuesday, four other candidates polling at 1 percent or higher — Lindsey Graham, Mike Huckabee, George Pataki and Rick Santorum — participated in an undercard debate. Of the original Republican candidates, Christie and Fiorina have been the only ones to make onto a main stage debate after dropping to the undercard debate.

Tuesday night marked the final debate of the 2015 calendar year. The next Republican Presidential Debate will be held Jan. 14, 2016, in South Carolina.