Ahead of Wednesday's vice presidential debate, FiveThirtyEight's presidential election forecast has Biden favored to win the election. The model gives the former vice president an 84 in 100 chance of wining in November and Trump a 16 in 100 chance of being re-elected.

FiveThirtyEight Politics Editor Sarah Frostenson told ABC News Live's "Your Voice, Your Vote: The Breakdown" it's hard to pinpoint one event that changed the polls due to the speed of the news cycle, but the economy and the last debate were two key factors.

"It was really the economy that was helping Trump the most," Frostenson said. "And so one reason why Biden is ahead out and doing so much better is Trump hasn't been able to deliver on economic promises here leading up to the election."

However, she said, voters still trust the president more than Biden on handling the economy.

As for last week's debate, Frostenson said that Biden got a "modest uptick" in the polls, but it caused a shift due to Biden's already sizable national lead.

"Going into this debate, you know, Pence and Harris aren't as well known as Biden and Trump, so there is a possibility that in seeing the number two candidates tonight, voters at home will be able -- who are still maybe on the fence -- to hear their messages and decide whether or not they're in Trump or Biden's camp," she said. "So it's not over for Trump yet by any means."

The vice president has been a steadfast gun-rights advocate and a supporter of the National Rifle Association (NRA), with a record that shows him opposing restrictions on the Second Amendment.

In 2010, Pence said "Congress should rebuff attempts to restrict the Second Amendment and recognize that programs such as national firearms registration and the assault weapons ban are antithetical to the constitutional rights of law-abiding Americans." Most recently, when Pence spoke at the National Rifle Association Leadership Forum in 2019, he told them "under this president and this administration, the right to keep and bear arms shall not be infringed."

During her presidential campaign, Harris has proposed executive actions to counter gun violence including banning assault weapons and near-universal background checks administered by people who sell over five guns a year. Gun manufacturers and dealers who fail to comply would have their licenses revoked. As the vice presidential nominee, she has called for the renewal of the assault weapons ban also called for the elimination of the "boyfriend loophole" in addition to her avid support of universal background checks.

"Before somebody can buy a lethal weapon, you might want to know if they've been found by a court to be a danger to themselves or others. You just might want to know," Harris told a crowd in Philadelphia in September. "These are the things about background checks, you just might want to know certain things before you give somebody something that can kill other human beings."

Harris told reporters in April 2019 that she owned a gun for "personal safety," but says it's a "false choice... to suggest you're either in favor of the Second Amendment or you want to take everyone's guns away."

-ABC News' Justin Gomez and Averi Harper

The Biden campaign released a statement from former President Jimmy Carter offering well wishes to Harris ahead of the vice presidential debate.

“We need champions in the White House like Joe Biden and Kamala Harris who understand the needs and values of working Georgians. Kamala Harris has the talent and charisma to lead our great nation as our next Vice President, and I know Americans will see that on full display during tonight's debate," Carter's statement read.

The longest-living president endorsed Biden’s presidential campaign in August.

-ABC News' Averi Harper

One thing that remains absent from Pence's speeches at campaign events is how he envisions providing health care for Americans. The Trump/Pence campaign in 2016 ran on a "repeal and replace" position of Obamacare and have repeatedly gone through the court system to try to dismantle the Affordable Care Act during their first-term. They have yet to put out a replacement plan since taking office.

Like Trump, Pence has also expressed the need to protect Americans with preexisting conditions, even though the Trump Administration is currently asking the U.S. Supreme Court to strike down Obamacare in its entirety, which already protects those vulnerable Americans.

As recently as September, during a town hall moderated by ABC News Chief Anchor George Stephanopoulos, Trump was pressed about his repeated claims to deliver a health care plan without following through. Trump said, "I have it already, and it's a much better plan," but he has not delivered.

On Sept. 24, Trump did sign several executive orders, framing them as his "America First Health Care Plan," which are not legislative proposals, but rather administrative actions. He claimed his new plans cost 60% less than options under Obamacare, an end to surprise billing and protections for Americans with preexisting conditions, which is already covered under the ACA.

Harris was initially a supporter of "Medicare for All" and backer of Sanders' plan which would get rid of private health insurance. During the presidential primary, Harris changed her position, instead calling for an expansion of health care access while still allowing for private health insurance. Harris, in an interview with Axios in October 2019, acknowledged that she'd been "called a flip-flopper for that."

As the Democratic vice presidential nominee, Harris has backed Biden's health plan which would provide a public option for Americans seeking health care and aim to lower costs.

-ABC News' Justin Gomez and Averi Harper

In light of President Trump's positive COVID-19 diagnosis and subsequent concerns from Harris' team, the Commission on Presidential Debates agreed to add additional safety precautions to Wednesday's debate at the University of Utah.

Unlike last week's presidential debate, everyone in the audience will be required to wear a face mask or covering and those who don't will be escorted out of the venue.

"They've got to wear a mask, and if they take their mask off they're gonna be escorted out, and I don't care who they are, they'll be escorted out," Frank Fahrenkopf, chairman of the Commission on Presidential Debates, told ABC News.

Harris and Pence will be tested prior to the debate, according to the commission, a change from the presidential debate when campaigns were responsible for testing their candidates and traveling parties.

And the candidates will be separated by more than just the issues -- or at least one of them will be.

After Pence's close proximity to others who have tested positive for COVID-19, the Harris campaign requested plexiglass barriers be used at the debate and the commission agreed -- but the Pence campaign said Tuesday that they never agreed to a plexiglass partition.

A senior administration official in Pence's office told ABC News Tuesday that the CPD decided to publicize the new safety protocols before any formal agreement was made and that the moderator and the Harris campaign can do as they want, "but we do not."

The official said Center for Disease Control and Prevention guidelines recommend plexiglass whenever 6 feet of separation isn't possible, but noted the candidates will be 12-feet apart on stage. The comment fell in line with Pence's chief of staff Marc Short who told The Washington Post Tuesday that plexiglass is "not needed."

Pence's communications director, Katie Miller, who tested positive for COVID-19 in May, also responded to the request in a statement to Axios earlier this week saying, "If Sen. Harris wants to use a fortress around herself, have at it."

Following news that Miller's husband, senior Trump aide Stephen Miller, tested positive for the coronavirus, she reportedly left Utah and a spokesperson declined to comment if Pence would agree to plexiglass.

-ABC News Justin Gomez, Averi Harper and Ben Gittleson