Democratic presidential contender Joe Biden on Thursday called a man in Iowa a "damn liar," "fat" and "too old to vote for me" after the man accused Biden without any evidence of getting his son Hunter a job with a Ukrainian gas company in exchange for access to the Obama administration.

"You're a damn liar, and that's not true," Biden snapped at the man during a campaign event in New Hampton, Iowa, as an audience of adults and children looked on.

The former vice president Biden then challenged the man — who had also questioned Biden's fitness for the White House given his age — to feats of strength, endurance and intelligence.

"I'm not sedentary," said the 77-year-old Biden. "You want to check my shape on, let's do push ups together, let's run, let's do whatever you want to do, let's take an IQ test."

Biden spokeswoman Symone Sanders later claimed that Biden said, "Look, facts," not "Look, fat," referring to the man, even though audio of the remark clearly sounds like "fat."

Sanders said in a tweet that "the gentleman is a self-identified Warren supporter who said he would vote for the VP in a general election ... his facts were flat-out wrong and .. the crowd backed VP Biden up in his response."

"Any assertion VP Biden said a word about the gentleman's appearance is making this something it is not. In the latter part of the exchange, the VP began to say, 'Look, facts,' then said, 'here's the deal,'" Sanders said.

"If you've been to a Biden event, you've heard this before."

The man, who refused to identify himself to NBC News, later told a reporter he would vote for Biden if he is wins the Democratic nomination for president.

The man said, "God no," when asked if he would vote for President Donald Trump.

"No, he's a first-class a--hole," the man said.

The man ignited Biden's ire with a comment that referenced President Donald Trump's pressuring of Ukraine last summer to investigate Biden and Hunter Biden in connection with Hunter's position on the board of the the natural gas company Burisma.