Biden's campaign announced his three guests to the debate: Kristin Urquiza, Gurneé Green and James Evanoff Jr.

The public first met Urquiza when she shared her story at the Democratic National Convention. She lost her father to COVID-19, and declared his "only pre-existing condition was trusting Donald Trump -- and for that he paid with his life." Urquiza is an environmental advocate at Mighty Earth and co-founded the awareness campaign "Marked by COVID."

Green is a small business owner from Cleveland Heights who was also highlighted during the Democratic National Convention. He owns the Cleveland Heights fashion boutique Chemistry 11. In addition to being a small business owner, Green is a certified health care information technologies analyst and a mother of two.

Evanoff is a service technician in Cleveland. He has eight years of seniority with United Steel Workers and works at ArcelorMittal, which was recently acquired by Cleveland Cliffs.

ABC News' Molly Nagle and Mary Bruce

Trump's first presidential debate with Hillary Clinton in 2016 set the record as the most-watched debate in television history, with 84 million viewers, surpassing the previous record of 80.6 million viewers set between Jimmy Carter and Ronald Reagan in 1980, according to Nielsen.

Trump's second debate with Clinton back in 2016 ranks as the ninth most-watched presidential debate with 66.5 million viewers.

MORE: Trump blames media after DNC tops RNC in TV ratings

On Sunday, a New York Times expose on President Trump’s tax returns revealed decades of tax avoidance and millions of dollars in business losses over the past two decades.

The picture painted by Trump’s returns is sharply at odds with the shrewd, deal-making image the president has tried to fashion as a real estate mogul and TV star on a show built around his business prowess, “The Apprentice.”

Now, five weeks from Election Day, the question is will these new revelations affect the presidential race?

Read the analysis from FiveThirtyEight's Geoffrey Skelley here.

When President Trump rang in 2020, the economy was one of his biggest selling points for reelection. He had inherited a strong economy from the Obama administration, and it continued to grow stronger during his first term. Unemployment was hovering at a 50-year-low, GDP growth was exceeding expectations and Wall Street was riding the longest bull market in its history.

But by spring, all of that came crashing down. While the economy has begun to shakily recoup some of its losses, a full and speedy recovery is anything but assured, making it a top concern for many Americans. According to a poll from the Kaiser Family Foundation released earlier this month, registered voters ranked the economy as the most important issue in deciding their pick for president, putting it ahead of the ongoing pandemic.

Trump is now trying to convince the country that since he oversaw a robust economy before the outbreak, he’s the best candidate to restore it. His opponent, Joe Biden, argues that Trump’s mishandling of the coronavirus compounded its impact on an economy that was inequitable to begin with and that it should be reimagined rather than rebuilt.

Click here to see how the candidates’ economic plans compare.

-ABC News' Shannon K. Crawford

Russia's ongoing brazen efforts to interfere in the presidential election -- as they did four years ago -- remains a principal concern among national security officials, along with other adversaries including China. But unlike in 2016, the rapid and sweeping embrace of vote-by-mail in response to the coronavirus pandemic injects new uncertainty about election security, as millions prepare to vote in an alternative way.

Fueling those anxieties over mail voting, which is underway in several states, is President Trump’s unsubstantiated allegations of rampant fraud, even as dozens of state election officials tell ABC News that they have confidence in the system. His campaign against vote-by-mail throughout the cycle exceeds similar efforts he made in 2016, when he argued, without evidence, that voter fraud was the only reason Hillary Clinton won the popular vote. His own voting integrity commission found no evidence of that.

The integrity of this year's matchup between Trump and former Vice President Joe Biden has taken on an outsized role in the increasingly competitive political environment, as attempts to undermine confidence in the democratic process mount both from outside the country's borders and from inside the Oval Office.

Biden has attempted to combat Trump’s onslaught by pointing out that Trump himself has voted-by-mail in Florida from the White House.

Some elections experts argue Trump’s offensive against mail-in voting is a voter suppression tool, which could lay the "groundwork for contesting a close election if he loses, " wrote Rick Hasen, a professor of law and political science at the University of California, Irvine, and the author of "Election Meltdown: Dirty Tricks, Distrust and the Threat to American Democracy."

"The most benign explanation for Mr. Trump’s obsessive focus on mail-in balloting is that he is looking for an excuse for a possible loss to his Democratic opponent, Joe Biden, in November. The less benign explanation is that he is seeking to sow chaos to drive down turnout and undermine the legitimacy of the election," wrote Hasen,.

At the first presidential debate on Tuesday at Case Western Reserve University in Cleveland, Ohio, the two rivals are set to spar over the integrity of the election, one of the topics previewed by the Commission on Presidential Debates.

Here's what we know about the candidates' histories with and stances on the issue

-ABC News' Kendall Karson and Quinn Scanlan