Joe Biden appeared to mix up Donald Trump and George Bush at a campaign event

• Democratic presidential nominee Joe Biden appeared to mix up President Donald Trump and former President George Bush on Sunday.
• Speaking at a virtual campaign event, he warned against "four more years of George" when telling people why they should vote for him. It's not clear which former president Biden was referring to.
• Biden has been open about his stutter and previously described himself as a "gaffe machine."
• On Monday, Trump seized on the gaffe to attack Biden on Twitter. His campaign has long sought to portray Biden as mentally unfit for office.
• In a separate Sunday interview, Biden said he was happy to have his mental and physical capabilities compared to Trump's.

Democratic presidential nominee Joe Biden appeared to mix up President Donald Trump and former President George Bush in a gaffe during a campaign event.

Biden was speaking with his wife, Jill Biden, at a virtual concert in support of his campaign on Sunday.

"Because of who I am running against, this is the most consequential election in a long, long, long time. And the character of the country, in my view, is literally on the ballot," he said.

"What kind of country are we gonna be? Four more years of George — George, uh, he, we're gonna find ourselves in a position where if Trump gets elected we're gonna be in a different world."

Jill Biden can be seen opening her mouth twice after Joe Biden said "George," but it is not clear if she was speaking. Some news outlets speculated that she may have been saying "Trump" to her husband.

You can watch the moment here, at 12 minutes and 20 seconds into the video:

It's not entirely clear which George Biden was referring to.

George W. Bush was president between 2001 and 2009, when Biden was a Democratic senator for Delaware.

Bush's father, George H.W. Bush, also served as president from 1989 to 1993. Biden ran for Democratic candidate for president in 1988, but did not get the nomination.

George was also the name of the first US president, George Washington, who served between 1789 and 1797.

Business Insider has contacted the Biden campaign for comment.

On Monday, Trump seized on the gaffe to attack Biden, saying: "Joe Biden called me George yesterday. Couldn't remember my name. Got some help from the anchor to get him through the interview."

"The Fake News Cartel is working overtime to cover it up!" the president also claimed. It's not clear what news outlets he was referring to.

Trump and his campaign have long sought to portray Biden as mentally unfit for office, jumping on any gaffes made by Biden and claiming them as evidence that Biden is senile or losing cognitive function.

But Biden has defended his mental acuity and has been open about having a stutter. In 2018, he even described himself as a "gaffe machine."

"I am a gaffe machine, but my God what a wonderful thing compared to a guy who can't tell the truth," he told an audience in Missoula, Montana, at the time.

In a separate interview on Sunday with CBS News' "60 Minutes," Biden said would be happy for people to compare his mental and physical performance to Trump's.

Anchor Norah O'Donnell said to Biden: "Donald Trump says you have dementia and it's getting worse," O'Donnell told Biden."

Biden responded by noting that Trump regularly makes errors, saying: "Hey, the same guy who thought that the 911 attack was a 7-Eleven attack. He's talking about dementia?"

"All I can say to the American people is watch me, is see what I've done, is see what I'm going to do," he added. "Look at me. Compare our physical and mental acuity. I'm happy to have that comparison."

In a town hall event earlier this year, Biden said of his stutter: "Things that people cannot control, it's not their fault. No one has a right, no one has a right to mock it and make fun of it, no matter who they are."