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.

TRUMP'S CLAIM: "Nobody knew where it was coming from, what it was. We've learned a lot. But Anthony said don't wear masks. Now he wants to wear masks."

FACT CHECK: Dr. Anthony Fauci, one of the top infectious disease experts in the country, and other public health experts initially told Americans not to wear surgical or N95 masks in the early days of what has become the COVID-19 pandemic.

At the beginning of the pandemic, the Centers for Disease Control and Prevention and the World Health Organization, as well as Fauci and other top experts, initially discouraged wearing masks because of concerns that masks and other personal protective equipment were in short supply for health care workers who needed them. Public health officials were also concerned wearing masks could have unintended consequences if people touched their face more often to adjust them or fail to keep social distancing.

"There was this feeling that there would be a shortage just for those who really need them very early on," Fauci said in a recent interview. "That was the big deal. We didn't have enough PPE including masks. Then it became clear that cloth masks worked reasonably well. And therefore there was no more shortage. Then the different analyses, meta analyses and others came in that in fact, it does work."

In early April, the CDC changed its recommendation about face coverings for the general public, based on evidence that a significant number of people who were asymptomatic or not yet feeling sick were transmitting the virus.

Duke University researchers have also concluded that "if 95 percent of people wear cloth masks when within 6 feet of other people in public, it will reduce COVID-19 transmission by at least 30 percent."

Trump also said he thought Fauci was a Democrat, but Fauci is not registered as a member of any political party, according to D.C. voting records.

-ABC News' Stephanie Ebbs and Arielle Mitropoulos