The final presidential debate has kicked off from Belmont University in Nashville marking Trump and Biden's final chance to pitch themselves to voters in primetime ahead of Nov. 3. The audience of roughly 200 people in stadium-style seating applauded as the candidates took the stage.

There was a last-minute change to remove the plexiglass partitions placed between the two candidates after Dr. Anthony Fauci weighed in and each tested negative for COVID-19. They remain socially distanced with at least 12 feet of space between them.

The first question from moderator Kristen Welker, NBC News White House correspondent, was on COVID-19 and went to the president.

Biden's mic will be muted while the president answers, and Trump's mic will follow suit when it's the former vice president's turn to weigh in.

"On behalf of the voters, I'm going to ask you to please speak one at a time. The goal is for you to hear each other and for the American people to hear every word of what you both have to say," Welker said.

Debate organizers removed the plexiglass barriers initially placed between the candidates’ lecterns after speaking with the government’s top expert on infectious diseases Dr. Anthony Fauci.

Fauci told ABC News Chief White House Correspondent Jonathan Karl that he got a call from Trump’s chief of staff Mark Meadows asking if in his opinion there was a need to have plexiglass between the two candidates.

Meadows then had Fauci talk to a doctor working with the Commission on Presidential Debates, and Fauci explained to the doctor that because the candidates were 12-feet apart, there was no need for plexiglass as droplets wouldn’t reach that far and aerosol isn’t stopped by plexiglass anyway.

Even with the removal of the plexiglass partitions, the coronavirus pandemic is still on display inside the debate hall at Belmont University in Nashville.

All audience members are required to wear masks and will be removed from the event if they refuse, organizers said. The mask requirement comes after several members of the Trump family removed their masks once seated at the first presidential debate in Cleveland.

Singer Kid Rock and professional golfer John Daly, both Trump supporters, were spotted in the audience ahead of the debate’s start without their masks. They put them back on after they were approached by debates staffers.

The FiveThirtyEight politics crew discusses how the last presidential debate might affect the election. Is there still time to shift opinions, or have voters already made up their minds?

In the wake of that canceled second showdown and a chaotic first debate before it, the Commission on Presidential Debates announced earlier this week it would mute candidates’ microphones at certain points Thursday to avoid interruptions and “maintain order.”

Trump and Biden will now have two minutes each of uninterrupted time to speak at the beginning of each 15-minute segment, of which there are six, in the 90-minute debate.

After the first four minutes of each segment, both of their microphones will go live for an “open-discussion portion,” the commission co-chair said. The moderator will not have control of the candidates' mics at any point. Those will instead be controlled by event production staff.

ABC News Chief Congressional Correspondent Mary Bruce said on ABC News Live Prime ahead of the debate, “Just because your microphone is down, doesn't mean that you necessarily will stop talking.”

Trump has attacked the integrity of the debate commission and its chosen moderators in recent weeks, deeming it all "crazy" and the new mic rule "very unfair” -- but sources have told ABC News Chief White House Correspondent Jonathan Karl that some advisers think muting the mics will actually help the president.

Biden, meanwhile, has called the muting of mics "a good idea" and said he’s expecting Trump to fire off personal attacks during their final showdown.

ABC News Chief Anchor George Stephanopoulos said the big question for Biden, who leads in nationwide polls, is whether he can close the deal with voters from Nashville. For Trump, it's how will he adjusts his performance after the "disastrous" first debate more than three weeks ago.

"Even the president's own aides called his blustering performance a self-inflicted wound," Stephanopoulos said.

The final topic of the night was climate change with Welker first asking each candidate how he would combat climate change and support job growth at the same time as president. Trump answered first.

"So we have the trillion trees program. We have so many different programs. I do love the environment, but what I want is the cleanest, crystal clear water, the cleanest air," Trump said, taking credit for the country's reduced carbon emission last year.

He went on to slam other counties air-quality and tout the U.S. by comparison.

"Look at China, how filthy it is. Look at Russia. Look at India. It's filthy. The air is filthy. The Paris Accord, I took us out because we were going to have to spend trillions of dollars, and we were treated very unfairly," Trump said, closing his two minutes by saying his administration has done an incredible job "environmentally."

When it was Biden's turn, he pivoted to the existential threat he says global warming poses to humanity and said the U.S. has a moral obligation to "deal with it" -- but said climate change also creates a prime opportunity for new jobs.

"Here's where we have a great opportunity. I was able to get both all the environmental organizations as well as labor, the people worried about jobs, to support my climate plan. Because what it does -- it will create millions of new good-paying jobs," Biden said. "Wall Street firms indicated that my plan -- my plan will, in fact, create 18.6 million jobs, 7 million more than his. This is from Wall Street. And I'll create $1 trillion more in economic growth than his proposal does. Not on climate, just on the economy."

Trump slammed Biden's response, claiming the former vice president's plan would cause a massive economic depression and deeming it a "pipe dream," before raising Biden's stance on fracking.

In the face of Trump's criticisms, Welker asked Biden directly, "Would you rule out banning fracking?"

"I do rule out banning fracking," Biden said. "We need other industries to transition to get to ultimately a complete zero emissions by 2025. What I will do with fracking over time is make sure we can capture the emissions from the fracking, capture the emissions from gas. We can do that and we can do that by investing money. It's a transition to that."

"Excuse me," Trump interrupted. "He was against fracking. He said it. I will show that to you tomorrow."

"Fracking on federal land, I said," Biden responded. "No fracking and/or oil on federal land."