Presidential candidate Joe Biden squared off with a voter in Iowa on Thursday, calling the man a "damn liar" after he accused Biden of helping to get his son on the board of a Ukrainian gas company in an attempt to win access with Ukraine's president.
In the testy exchange at a town hall packed with Biden supporters, the former vice president took umbrage with another accusation from the voter: that Biden is too old to run for president.
Biden, who is 77 years old, responded by challenging the voter to a pushup match, a running competition and an IQ test — offers that were greeted with audience applause.
Biden then moved to defending his son, Hunter, who previously served as a board member of the Ukrainian energy company Burisma.
Hunter Biden is a frequent target of President Trump's attacks amid the impeachment inquiry. The House investigation has documented a campaign led by Trump's personal attorney, Rudy Giuliani, to pressure Ukraine to announce it was opening an investigation into the younger Biden.
Biden's son has never been accused of any legal wrongdoing related to his time in Ukraine, a point Biden made loud and clear to the voter.
"Nobody has said my son has done anything wrong," Biden said. "And nobody has ever said it," he said, before the voter chimed in: "I didn't say you were doing anything wrong."
To this, Biden raised his voice and invoked a stern tone, saying, "You said I set up my son to work on an oil company. Isn't that what you said? Get your words straight, Jack!"
At one point, a staff member attempted to take the microphone away from the voter, but Biden said, "Let him go, let him go."
WATCH: A tense exchange with a voter at @JoeBiden’s event in New Hampton, IA this morning, where a voter started out by telling Biden he had two problems with him: he was too old, and his son’s work in Ukraine pic.twitter.com/ok7m0ShFPd— Molly Nagle (@MollyNagle3) December 5, 2019
Biden then said that the reason he is running for president is he "has been around a long time" and he "knows more than most people know."
After the nearly two-minute back-and-forth, Biden said, "I'm not going to get in an argument with you, man."
The voter then said Biden doesn't "have any more backbone" than Trump does. The comment elicited boos from the crowd.
Before sitting down, the man said he was not planning to vote for Biden. And Biden quipped back: "Well, I knew you weren't, man." Biden said, "You're too old to vote for me."
The voter refused to provide his name to reporters but said he is an 83-year-old retired farmer.
The confrontation comes amid a week in which Biden otherwise appeared to be strengthening his standing as the Democratic front-runner.
California Sen. Kamala Harris, a candidate who once seemed to pose a strong challenge to Biden among two key groups in his base — African Americans and the party's establishment — dropped out of the race on Tuesday.
Biden also picked up the endorsement of a well-known Democrat, former Secretary of State John Kerry.
Biden has a long history of confronting voters who challenge him on the campaign trail. In 1987, amid questions that Biden had inflated his college and law school résumé, Biden told a voter who asked about the matter that "I think I probably have a much higher IQ than you do."
Last month in South Carolina, Biden told immigration activist Carlos Rojas that he "should vote for Trump" when Rojas criticized the Obama-Biden administration for its deportation record.
Soon after, the most senior Latina on his staff quit. Vanessa Cárdenas was reportedly frustrated by both a lack of input and Biden's rhetoric on immigration.