Making his closing campaign message before Election Day, the Democratic presidential nominee began with a well-used introduction, saying he was “Jill Biden’s husband”.
But, as he laughed, the 77-year-old went on to say he was also Kamala Harris’s running mate.
“My name is Joe Biden and I’m Jill Biden’s husband, and I am Kamala’s running mate,” he told an audience. ”You think I’m kidding, don't you.”
Republicans seemed oblivious to the retort against Mr Trump, who told Sean Hannity in a recent appearance that Ms Harris would assume the presidency within “three months”.
“Joe Biden confirms what we all knew,” wrote White House press secretary Kayleigh McEnany on Twitter, as she shared an edited clip of Mr Biden’s speech.
She also pointed to the words “Kamala” that were seen on a backdrop behind Mr Biden, and suggested that was suspicious, despite the signage reading: “Joe and Kamala”.
Kyle Becker, a former producer at Fox News, added: “Voters might want to brush up on the most socialist senator from California, Kamala Harris, before casting their votes for her running mate Joe Biden.”
Mr Trump has spent months attempting to paint Mr Biden as docile and susceptible to progressive Democrat control, in an appeal to Republican voters.
Despite those claims, Mr Trump continues to trail the Democrat in national opinion polls, while states such as Georgia — where Mr Biden spoke on Tuesday — have become competitive.
If Mr Biden does win the 3 November election, Ms Harris will become the United States’ first female vice president, as well as the first of Black and South Asian heritage.