Republican presidential debate as it happened: Which candidate will come on top during the fourth debate?

And that's a wrap for the fourth Republican debate. The next debate, for Democratic candidates Hillary Clinton, Martin O'Malley and Bernie Sanders will be held on 14 November. It will be followed a month later with the fifth GOP debate on 15 December.

The candidates begin their closing statements, with several candidates attacking Clinton and fellow Democratic candidate Bernie Sanders. Here's a look at the top searched Republican candidates during this debate.

Senator Paul is asked about President Obama's climate change policies. Paul says that global warming is not only caused by humans but also by nature.

The candidates take turns attacking Hillary Clinton, as the debate begins to wrap up.

Cruz is asked if he would let a big bank, like a Bank of America, fail. He responds that he wold not bail the bank out and would essentially let it fail.

Carson says he would not break up big banks. Says he opposes Dodd-Frank and receives the support of Rubio.

Democratic frontrunner Clinton has taken to Twitter to tweet in both English and Spanish.

Donald Trump is booed for a second time when he hits at Carly Fiorina, asking, "Why does she keep interrupting us?" The candidates continue to discuss Russia and the ongoing crisis in the Middle East.

Trump says he supports Russia's Putin bombing the Islamic State. When Bush attempts to correct him, Trump says that Isis did in fact bomb Russia. Adds that the US should not be policing the world.

Bush hits back says that the US should enforce a no-fly zone above Syria and that the US should not support Syria's Bashar al Assad nor Putin. Fiorina jumps in and says she would rebuild many US military bases around the world and send more troops to Germany.

Carson, who in the past has struggled to answer questions regarding the economy and foreign policy, is asked about terrorism abroad. He responds: We have to make terrorists "look like losers."

Senator Rubio attacks Senator Paul "as a committed isolationist" after Paul calls him "not very conservative."

Marco! Marco! Marco! How is it conservative to add a trillion dollars that we can't even pay for?

-Rand Paul

Yes, I have a child tax credit increase and I'm proud of it.

- Marco Rubio

A brief Google Trends look at the undercard debate:

Trump, the most vocal against immigration reform, is asked about the appeals court decision to uphold a block against President Obama's immigration plan. The frontrunner said he is happy and reiterated he wanted to deport the 11 million undocumented immigrants in the US. Meanwhile, Kasich hits back calling Trump's plan "silly".

Ben Carson is asked about recent criticisms about anecdotes regarding his life. The retired neurosurgeon says that while he understands the vetting process, he would be okay if it happened to all candidates. He then deflects the question by attacking Hillary Clinton and the Benghazi scandal.

The lone female candidate on the Republican side, Carly Fiorina, gets perhaps the loudest applause when she says that corrupt politics need to be broken down.

Jeb Bush, who was originally slated as the favourite to win the nomination, has steadily declined in the polls. The former Florida governor appears to be slightly fiery tonight, arguing that he only got 4 minutes to talk during the last debate. Twitter was quick to respond.

Kasich, the governor of Ohio, calls for balancing the budget and takes another hit against his GOP opponents for their radical tax plans.

Marco Rubio says that raising the minimum wage would make people more expensive than people. The Florida senator instead says instead the US should make it easier to open businesses and that job training, including vocational schools, should be the focus.

First question is focused on raising the minimum wage to $15 an hour. Frontrunner Donald Trump says that he does not support raising the minimum wage. Ben Carson, meanwhile, says that people need to be educated about the minimum wage. Carson, who has given Trump a run for his money, said, "Every time we raise the minimum wage, the number of jobless people increases. It's particularly a problem in the black community."

We're minutes away from seeing the top eight Republican candidates debate for the fourth time this campaign season. Candidates are being introduced as the debate that will focus on the US economy begins.

Candidates are giving their closing statements, more than 10 minutes after the debate was scheduled to end. In his final statement, Chris Christie takes a final shot against Clinton, calling her out for saying that her greatest enemy are Republicans.

We'll be back at 9pm ET/2am GMT for the main debate.

Santorum is asked to comment on the VA's healthcare system. He says the system is antiquated and that veterans should be allowed to move into the private insurance sector.

The first undercard debate of the night is winding down, with the main debate scheduled to air at 9pm ET/ 2am GMT.

Huckabee says the Fair Tax makes a "heckuva lot more sense."

Do you know an American who will just stop spending? I don't.

The candidates are asked who they most admired among Democrats.

• Jindal: Refused to answer. Says everyone in Washington should be sacked.
• Huckabee: Also refused to answer. Focuses on Veterans Day and the mess at Veterans Affairs.
• Christie: Continuing the trend, also refuses to answer but instead attacks Democrats for their alleged lack of support for law enforcement.
• Santorum: Says he respects Democrats for their willingness to fight for what they want and win.

Jindal gets an audible gasp from the audience after he continuing his assault against Christie:

Chris, I'll give you a ribbon for participation & a juice box.

While Christie has attacked Democrats and has attempted to remain positive towards his fellow Republican opponents. However, Jindal says that Christie's record does not make him a viable GOP nominee.

Christie asked about Chinese cyber espionage and he places the blame on President Barack Obama and former Secretary of State Hillary Clinton. The governor says that if Beijing attempts to spy again, the US will retaliate.

The debate moves on to the refugee crisis in Syria. Huckabee says the US cannot afford to open the doors to Syrian refugees. He says the US should help the refugees closer to Syrian and that the country should pressure Saudi Arabia to help the crisis in Syria.

Jindal calls out his fellow Republican candidates, saying he has been the only governor who has cut spending at a state level. Huckabee hit back saying that he and his fellow governors have all had to make difficult spending decisions. Jindal says that Huckabee's record says otherwise. Meanwhile, Christie says that if voters are worried about Huckabee or Jindal, they should really be worried about Democratic frontrunner Hillary Clinton.

Republican candidate Jim Gilmore, who has not qualified for the last two debates, is also tweeting during the debate.

Rick Santorum says he wants to change the tax code to be pro-family. His comments are met by applause from the audience.

Rick Santorum takes the mic next, focuses on training for employment and updating the tax code. Meanwhile, Bobby Jindal is asked about oil prices and its effect on jobs growth. Jindal, like the three candidates before him, attacked President Obama's alleged failure on unemployment.

Up next is Mike Huckabee, who also says he would reform the tax code. Huckabee says he does not understand why the US should move away from manufacturing jobs and instead should push to return jobs to the US. Huckabee also calls for doing away with the IRS (Internal Revenue Service).

The first question is directed towards New Jersey Governor Chris Christie who is asked about the level of unemployment in the US. He says he will reform the tax code, remove special interest rates and reduce regulation on small businesses.

The four candidates of the undercard debate have taken the stage for the one hour debate. Candidates have been told that if they go over their allotted time, they will hear a buzzer.

The undercard debate is set to start in a few minutes, with four Republican candidates facing off. We'll be live tweeting throughout the undercard and main debates tonight, so be sure to stay tuned.

New Jersey Governor Chris Christie, along with former Arkansas Governor Mike Huckabee, were demoted to the undercard debate after poor polling performances. Both candidates failed to earn the 2.5% average polling threshold to make the main debate and were pushed to the earlier forum. Christie, who has struggled to gain momentum during his campaign, tweeted, "It doesn't matter the stage, give me a podium and I'll be there to talk about real issues."

Meanwhile, South Carolina Senator Lindsey Graham and former New York Governor George Pataki were also demoted and were unable to qualify for either debate. Graham's campaign blasted the change, with his campaign manager saying, "In the end, the biggest loser tonight is the American people and the Republican Presidential primary process that has been hijacked by news outlets."

The latest poll by McClatchy-Marist reveals Washington outsider Ben Carson is leading Republicans with 24%. He is followed closely behind by Donald Trump with 23% and Marco Rubio with 12%. However, a poll by Fox News placed Trump in first with 26%, Carson in second with 23% and Rubio tied in third with Ted Cruz with 11%.