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To win the presidency, candidates have to hit the magic number of 270 electoral votes. The Electoral College comprises a total of 538 members, with each state getting a total number of electoral votes equal to its congressional delegation and three additional electoral votes for District of Columbia.

American foreign policy for over half a century was defined by its bipartisan nature, symbolized in the old adage that politics stopped at the water's edge.

But in recent years, foreign policy has become as politically charged as virtually everything else in American life, and when voters mail in their ballots or go to the polls, they'll face a stark difference between the Republican and Democratic nominee and their views of the world and the United States' place in it.

Ahead of Thursday's debate, the Trump campaign made an eleventh-hour demand that the questions focus on foreign policy, as opposed to the topics chosen by the moderator, though the campaigns agreed months ago to allowing the moderator to choose the debate topics.

Read about how Trump and Biden differ on major foreign policy issues including relations with China, Iran, North Korea and NATO allies, among others, here.

-ABC News’ Conor Finnegan

Aides to Trump and Biden separately reported their candidates tested negative for COVID-19 ahead of the final debate.

Earlier Thursday, White House press secretary Kayleigh McEnany told reporters that Trump had tested negative, and Trump’s chief of staff Mark Meadows said the president was tested during the flight from the Washington, D.C., area to Nashville.

They did not offer information on whether the people who accompanied Trump to Nashville -- including Ivanka Trump, Jared Kushner, Tiffany Trump, Bill Stepien, David Bossie and Robert O’Brien -- were tested.

At a NBC News town hall last week, Trump claimed he didn’t remember whether he’d been tested on the day of the first debate, which took place before his first positive COVID-19 test was reported.

-ABC News' Molly Nagle and Jordyn Phelps

Atlanta Mayor Keisha Lance Bottoms tweeted Thursday that she will be attending the presidential debate as a guest of Biden. Bottoms also tweeted that she was a guest at the first debate in September.

Other guests of the former vice president include small business owners Zweli and Leonardo Williams of Durham, North Carolina. Biden campaign senior adviser Symone Sanders said the campaign invited them to draw attention to the struggles of small business owners.

“These small business owners from Durham -- because these are much like small business owners from Wisconsin, like the small business owners down in Georgia, like small business owners all over this country -- who are grappling with how to make ends meet, how to continue to provide, not only for their families but their employees. They're making decisions that, frankly, they shouldn't have to make because the president failed them,” Sanders said.

-ABC News’ John Verhovek and Beatrice Peterson.

TRUMP'S CLAIM: “When I closed, he said, 'This is a terrible thing. You're xenophobic.' I think he called me racist, even, and -- because I was closing it to China. Now, he says I should have closed it earlier. It just -- Joe, it doesn't work."

FACT CHECK: While Trump claimed that Biden opposed his decision to ban most travel from China at the outset of the coronavirus pandemic and that he called the restrictions "xenophobic," the former vice president did not explicitly weigh in on the decision when it was announced on Jan. 31. He did call the president xenophobic minutes after the partial travel ban was announced, but did not call Trump a racist for the decision.

During a campaign event that same day in Fort Madison, Iowa, Biden discussed the growing concern over the COVID-19 outbreak and cautioned that Trump should let science "lead the way."

"In moments like this, this is where the credibility of a president is most needed as he explains what we should and should not do," Biden told the crowd at the event. "This is no time for Donald Trump's record of hysterical xenophobia ... and fear-mongering to lead the way instead of science."

The comments came just minutes after the White House announcement, so it was unclear if Biden was referring to the decision specifically, but the former vice president did tweet a similar sentiment the next day.

"We are in the midst of a crisis with the coronavirus," Biden posted. "We need to lead the way with science -- not Donald Trump's record of hysteria, xenophobia, and fear-mongering. He is the worst possible person to lead our country through a global health emergency."

Throughout March, Biden used the word "xenophobic" in various speeches and tweets to criticize the president labeling COVID-19 as the "China virus."

Biden did acknowledge the travel restrictions put in place by the Trump administration in a March speech, noting they "may" slow the spread.

"Banning all travel from Europe or any other part of the world may slow it, but as we've seen, it will not stop it. And travel restrictions based on favoritism and politics rather than risk will be counterproductive," Biden said.

Biden's campaign did not explicitly discuss the vice president's view of the ban until April.

"Joe Biden supports travel bans that are guided by medical experts, advocated by public health officials and backed by a full strategy," Biden's deputy campaign manager Kate Bedingfield told CNN. "Science supported this ban, therefore he did too.

-ABC News' Molly Nagle