Moderator Susan Page posed the first question to Harris, revealing the first of nine topics: The coronavirus pandemic.

Noting the president's recent diagnosis, Page asked Harris, "What would a Biden administration do in January and February that a Trump administration wouldn't do?"

True to her form as a prosecutor, Harris -- the first Black woman and first Indian American to take a vice presidential debate stage -- laid out her facts, arguing the administration knew about the threat of the virus in January but didn't act soon enough.

"They were informed that it's lethal in consequence, that it's airborne, that it will affect young people," Harris said. "They knew what was happening and they didn't tell you."

Harris then said the Trump administration still doesn't have a plan.

"Well, Joe Biden does and our plan is about what we need to do around a national strategy for contact tracing, for testing, for administration of the vaccine, and making sure that it will be free for all," she said.

There was no handshake between candidates -- customary at the top of such events -- due to COVID-19 precautions. The audience, limited to under 100 attendees, applauded Pence and Harris as they took the stage.

Former Democratic 2020 presidential candidate Pete Buttigieg, who played Pence at some mock debate rehearsals for Harris, was also spotted in the audience.

Pence and Harris have taken the stage in Salt Lake City for the vice presidential debate. The candidates skipped the traditional handshake due to COVID-19 and are divided by plexiglass.

Harris' chief of staff Karine Jean-Pierre told ABC News Chief Anchor George Stephanopoulos that Harris won't spend the night fact-checking Pence on stage.

Instead, the former prosecutor will "bring the case forward" on how Biden and Harris could lead to a different America.

"This debate is about Donald Trump's failure to contain COVID-19, and not just that but to also help working families," said Jean-Pierre, adding Harris has a "very diverse team" that has prepared her for the debate.

Jean-Pierre also criticized the example Trump has set since testing positive for the novel coronavirus last week.

"You have a president right now when he left the White House, he decided that he was going to make a campaign by removing his mask. His rhetoric has been incredibly dangerous," she said. "As Joe Biden said, it's a tragedy that he believes that he was blessed to have this virus, when people are suffering."

Marc Short, Pence's chief of staff, noted that Harris, like Pence, is "also a very skilled debater and has a record as a prosecutor, so I think it will be a very engaging conversation for the American people and hopefully one that shows a clear contrast in visions between the two campaigns."

Short said Pence will argue the case that the Trump administration protected more American lives in its COVID-19 response.

With less than a month to go until the election, early voting has already begun in 33 states and at least 5.5 million votes have been cast -- hitting record numbers across the nation.

According to the United States Elections Project, spearheaded by the University of Florida's political expert, Michael McDonald, an unprecedented 5,618,155 voters have already voted and at least 69,786,179 ballots have been requested in early voting states.

The coronavirus pandemic plays a factor in explaining the large early voting numbers as well as an increase in voter interest. Voters in 2020 are more eager to cast a ballot ahead of Election Day where polling sites could be viewed as overcrowded during pandemic standards.

Seven states --- California, Colorado, Hawaii, Nevada, Oregon, Utah and Washington -- have an all-mail ballot election meaning anyone registered to vote automatically receives a ballot to their registered address.

-ABC News' Kelsey Walsh

If Wednesday night showcases Sen. Kamala Harris the prosecutor, consider the new evidence added to her case.

And if Vice President Mike Pence is cast as the best explainer and defender of Trumpism, consider how much harder his job has become.

It's been eight short but incredibly long days since the first presidential debate. Since then, President Donald Trump has struggled to denounce white supremacism; refused to commit to accepting the results of the election; spread falsehoods about the voting process; been diagnosed with COVID-19, amid a full-fledged Washington outbreak; choreographed a triumphant return to the White House to urge the nation not to let the pandemic "dominate"; pulled the plug on further coronavirus relief talks until after the election and then reconsidered the move in some late-night tweets.

Enter the number twos -- in a campaign where there's seldom been more attention on the potential need for their services.

Pre-debate squabbles in Salt Lake City include fighting over plexiglass partitions and more space between the candidates to accommodate social distancing. What's really separating the vice-presidential candidates, though, are campaigns of the men at the top of the ticket -- who have distinct styles that are nothing like those of their running mates or each other.

Four years ago, it was Pence holding steady and calm in a debate with a feisty Sen. Tim Kaine, who faced blowback for his interruptions in a mild-mannered affair. Just last year, Harris' main debate opponent was the man she now shares a ticket with -- bringing set-piece attacks that appeared to nick former Vice President Joe Biden.

Now, amid the chaos of the moment and the relative stability of the campaign, Harris will bring a case that Pence might be uniquely equipped to defend.

-ABC News' Political Director Rick Klein