Businessman Donald Trump, Sen. Marco Rubio (R-FL), Sen. Ted Cruz (R-TX) and Gov. John Kasich (R-OH) were in attendance at the debate.

From the Flint water crisis to the U.S. economy, the discussion lit up with banter between Trump and Rubio for most of the night with Cruz occasionally chiming in. 

All the while outside the theater, protesters for Flint called for Gov. Rick Snyder's arrest.

Here are the stances each candidate took on most of the key issues discussed at last night's debate. 

Donald Trump

Trump addressed two talking points of his campaign, the New York Times off the record discussion and the Trump University lawsuit.

Cruz called on Trump to release the recording of his conversation with the New York Times about immigration. Trump refused and said he wants to keep his conversation between the Times and himself.

"I may have discussed something like that with the New York Times, but I would never release off-the-record conversations," Trump said.

The other nominees objected to his refusal.

"If we nominate Donald, we're going to spend the spring, the fall and the summer with the Republican nominee facing a fraud trial," Cruz said.

Trump also addressed Mitt Romney's comments about him and said he was a failed candidate. In addition, he denounced the Ku Klux Klan and David Duke during the debate.

Recently, Trump won seven states on Super Tuesday — more than any other nominee.

Rubio, Cruz and Kasich all vowed to support Donald Trump if he were to win the Republican nomination.

Ted Cruz

Topics Cruz discussed during the debate included immigration and his plan to repeal Obamacare.

Cruz said the immigration system in the U.S. needs to be reformed.

"If you are one of the 65 to 70 percent of Republicans who recognize that nominating Donald would be a disaster, then I ask you to come join us," Cruz said. 

The candidates talked about the city of Detroit and its legacy.

"Detroit is a great city with a magnificent legacy that has been utterly decimated by 60 years of failed left-wing policy," Cruz said.

He blamed Democratic policies for driving out Detroit citizens nearly 50 years ago. Cruz also said former president Ronald Reagan is an example of what the American people need now.

"I think the American people understand that yelling and cursing at people doesn't make you a tough guy," Cruz said.

On immigration, Cruz said he does not want to deport people. 

"I'm not going to build a wall, I'm not going to deport people, this is all just rhetoric for the voters," Cruz said. 

Recently, Cruz won four states in the primary elections. 

Marco Rubio

A majority of Rubio's dialogue during the debate was in response to or discussing Trump.

Rubio said Trump will not be able to go far in the candidacy.

"Of all the people on this stage, he performs the worst against Hillary Clinton," Rubio said.

He called out Trump's company and overseas presence and Trump fired back by saying Rubio has not employed one person. 

When the group discussed immigration, the policy set Rubio apart.

"As far as my record on it is concerned, I absolutely want to solve this issue," Rubio said.

Trump changed his harsher view on immigration. He agreed with Rubio about keeping highly skilled workers in the U.S.

"We need highly skilled people in this country," Trump said. "We'll get them in."

Rubio went after Trump for his workers who have work visas.

"When you bring someone in on one of these visas they can't go work for anybody else," Rubio said. "They either work for you or they have to go back home."

The candidates eventually discussed the Flint water crisis.

"What happened in Flint was a terrible thing," Rubio said. "It was systemic breakdown at every level of government."

Rubio said politicizing the issue in Flint is wrong.

"I will say, I give the governor credit," Rubio said.

John Kasich

Kasich spent most of the debate expressing his campaign's work to unite both parties instead of fighting.

"I know how to bring people together, Republicans and Democrats," Kasich said.

He was the only nominee to bring up the problem of student debt for college students. He said the debt will ultimately cause problems for the U.S. economy.

"Their sons or daughters are living in the basement because they can't get a good job after they rang up so much college debt," Kasich said.

Nearly 7 million people discussed the economy on Facebook, according to Fox News, who partnered with the social media site during the debate.

Kasich and other nominees commented on the minimum wage. He said he is not for a federal minimum wage increase but for states to handle it the way he has in Ohio.

"There's people in this country ... their wages haven't gone up for so long," Kasich said.