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

HARRIS' CLAIM: "Joe Biden has been so incredibly transparent, and certainly by contrast, the president has not. Both in terms of health records, but also let's look at taxes. We now know because of great investigative journalism that Donald Trump paid $750 in taxes. When I first heard about it, I literally said, you mean $750,000? And it was like, no, $750. We now know Donald Trump owes and is in debt for $400 million."

PENCE'S CLAIM: "The president said those public reports are not accurate and the president's also released literally stacks of financial disclosures the American people can review just as the law allows."

FACT CHECK: As a presidential candidate in 2016 and as a sitting president since, Donald Trump has released annual financial disclosure reports filed to the Federal Election Commission and the Office of Government Ethics, as required by federal laws. Trump's annual personal financial records, which are nearly 100-pages each, show his source of income, other assets, as well as liabilities.

Trump, however, has not released his personal tax records, which is not required by law but has been a decades-long tradition that has been followed by his predecessors in the White House.

Biden and Harris have differentiated themselves from Trump by releasing their federal and state tax returns -- most recently just last week, showing Biden and his wife paid roughly $290,000 in taxes to the federal government in 2019, and Harris and her husband paid about $1.2 million in federal and state taxes last year.

Harris' claim that Trump paid just $750 in taxes comes from The New York Times' recent report. According to the Times, Trump's tax records show that he paid just $750 in federal income taxes the year he ran for president and his first year in the White House.

The report also stated that Trump is personally responsible for loans and other debts totaling $421 million, "with most of it coming due within four years."

--ABC News' Soorin Kim