Biden's campaign pulled down more than $12 million during the 90-minute vice-presidential debate between Kamala Harris and Mike Pence

• Democratic presidential nominee Joe Biden's campaign pulled in more than $12 million on Wednesday night during the only vice-presidential debate of this election season, Politico reported.
• Biden's campaign also broke fundraising records following his debate with President Donald Trump last week, raking in $10 million.
• The 2020 presidential election is expected to be the most expensive election in modern US history.

Democratic presidential nominee Joe Biden's campaign pulled in over $12 million from grassroots donors on Wednesday night, during the only vice-presidential debate between his running mate Kamala Harris, and Vice President Mike Pence, a Biden campaign aide told Insider.

Politico first reported the news.

Biden's campaign also broke fundraising records following of his debate with President Donald Trump one week earlier. At that time, Biden had raked in almost $10 million in three hours around the time of the debate.

The democratic nominee has been outpacing Trump in fundraising and campaign spending in recent months.

In the two days after Biden named Harris as his running mate, his campaign received $48 million in donations, Politico reported.

Biden raised $365 million in August, and while the figures for September have not been released yet, a person familiar with the issue told Politico the fundraising haul for that month is expected to be higher.

The vice-presidential debate featured a number of highlights for Harris, who criticized the Trump administration's handling of the COVID-19 pandemic.

"The American people have witnessed what is the greatest failure of any presidential administration in the history of our country," Harris said. "And here are the facts: 210,000 dead people in our country in just the last several months ... one in five businesses are closed. We're looking at frontline workers who have been treated like sacrificial workers."

Pence told her to "stop playing politics with people's lives."

Harris also called out Trump over reports that he paid only $750 in federal income taxes in 2016 and 2017, and jabbed Trump over his other financial liabilities.

"We now know Donald Trump owes and is in debt for $400 million — and just so everyone is clear, when we say in debt, it means you owe money to somebody," Harris said.

And notably, a fly buzzed around the debate stage, landed on Pence's head, and stayed there for at least two minutes. Biden's campaign sold $10 fly swatter bearing the slogan "Truth Over Flies." The fly swatters sold out almost immediately.

The Biden campaign also broke last week's record for concurrent users on the voter-registration site, IWillVote.com, a site paid for by the Democratic National Committee, the Biden campaign aide told Insider.

"Last night's traffic was more than 1/3 of the traffic for the entire month of September in one night," the aide said.

"In the past 24 hours, there have been 18,000 vote by mail submissions, Over 6,000 people told us they would like to vote in person, and 12,500 took the first step to registering to vote."