The showdown came as President Donald Trump and several in his orbit have tested positive for the novel coronavirus, raising questions on a transfer of power to the vice president were Trump at 74 -- or Democratic nominee Joe Biden at 77 -- to become too ill to serve.
The debate's format was divided into nine 10-minute sections with each candidate having two minutes to respond to the opening question in each segment and the remaining time allowed for follow ups. Moderator Susan Page, Washington Bureau chief of USA Today, did not release the topics in advance.
The sole vice presidential debate follows Trump and Biden's chaotic debate last week in Cleveland.
Here is how the news is developing today. All times Eastern.
Oct 07, 2020, 1:18 PM EDT
Pence tests negative for COVID-19 on Wednesday
Vice President Mike Pence tested negative for the coronavirus on Wednesday, according to his office.
President Donald Trump and Vice President Mike Pence arrive in the Rose Garden to speak on Covid-19 testing at the White House in Washington, D.C., Sept. 28, 2020.
Mandel Ngan/AFP via Getty Images, FILE
Pence’s office said on Tuesday that the vice president had gotten a negative PCR test Tuesday afternoon and negative rapid test Tuesday morning -- Pence had also gotten a negative PCR test Monday. Pence's most recent negative result was from an antigen test.
Pence’s office has not responded to questions about what type of test members of the vice president's group attending the debate were using.
Sen. Harris also tested negative for COVID-19 on Tuesday.
-ABC News' Ben Gittleson and Averi Harper
Oct 07, 2020, 1:07 PM EDT
Inside Pence debate prep: 'On-message Mike' forced to defend Trump’s handling of coronavirus
While President Donald Trump resisted typical debate preparations, Vice President Mike Pence has held lengthy mock debate sessions and enlisted the help of a former prosecutor and state attorney general to play his opponent.
Former Florida Attorney General Pam Bondi -- who was also a member of the president's impeachment defense team -- was tasked to play the role of Sen. Kamala Harris in mock debate sessions with Pence in Washington, D.C. before he left for Utah.
Bondi is a career prosecutor who has a history with Kamala Harris -- both served as state attorney generals.
"Kamala was my colleague when we were attorneys general together and she's very smart, she's a seasoned debated, you know she's career prosecutor so prosecutors can debate and they can debate well," Bondi told Fox News.
While top aides privately call Pence "on-message Mike," referring to his more measured, consistent tone, he will be forced to defend the Trump administration's handling of the coronavirus pandemic as the president suggests his contracting COVID-19 was an act of political courage to help him lead the fight against the virus.
Aides plan to use Pence's experience as the head of the White House coronavirus task force to frame him as being on the "front lines" of fighting for the American people on COVID-19.
Scott Walker, former governor of Wisconsin, speaks during the Conservative Political Action Conference (CPAC) in National Harbor, Md., Feb. 28, 2019.
Aaron P. Bernstein/Bloomberg via Getty Images, FILE
Former Wisconsin Gov. Scott Walker has also been advising Pence. Walker helped Pence prepare for the last vice presidential debate against Sen. Tim Kaine in 2016.
Walker told Fox & Friends on Wednesday that there's no doubt Pence will face questions on COVID-19, but will focus on how the administration took quick action -- including shutting down China travel.
Walker said Pence will be "calm" but also "emotional and aggressive" during Wednesday's debate.
-ABC News' Rachel Scott and Katherine Faulders
Oct 07, 2020, 12:39 PM EDT
Pelosi tells Harris to 'be yourself'
House Speaker Nancy Pelosi told reporters Wednesday that she's been texting with Sen. Kamala Harris about tonight's vice presidential debate.
Her advice to Harris: be yourself.
House Speaker Nancy Pelosi conducts her weekly news conference in the Capitol Visitor Center on Oct. 1, 2020.
Tom Williams/CQ-Roll Call via Getty Images
She also noted that health care will be a big topic tonight and encouraged Harris to beat that drum loudly.
-ABC News' Mariam Khan
Oct 07, 2020, 12:16 PM EDT
Mike Pence: Everything you need to know
Vice President Mike Pence represents a more traditional style of the Republican Party compared to President Donald Trump but has been a loyal second-in-command throughout their first term in office. Pence has been at the forefront, sometimes leading, major policy efforts of the Trump administration, such as the White House's response to the coronavirus pandemic.
The pair did not personally know one another prior to their 2016 race, but their first term has strengthened their bond. Pence has been steadfast in his support for the president through controversy, whether it was a ban on travel into the U.S. from predominantly Muslim countries, Trump's impeachment by the House of Representatives and trial in the Senate, or the decision to resume large, in-person campaign events amid coronavirus.
