As Joe Biden fights for the 2020 Democratic nomination, the former vice president has had to contend with some major vulnerabilities, from his age to his son Hunter’s dealings in Ukraine, which Donald Trump and his allies have seized on in an attempt to deflect impeachment efforts. On Thursday, a voter in Iowa confronted Biden about both of these issues—and Biden did not handle the criticism well. The 83-year-old voter told Biden at a campaign event that he was “too old for the job,” before turning to Ukraine and accusing Biden of “selling access to the president just like [Trump] does.” Biden cut in with a strong response, telling the voter, “You’re a damn liar, man.”

Biden insisted that “No one has said my son has done anything wrong and I did not on any occasion,” after the Iowa voter raised objections to how Biden had “sent your son over [to Ukraine] to get a job and work for a gas company that he had no experience with gas or nothing in order to get access for the president.” (There is no evidence to support allegations that Biden improperly used his political influence to benefit his son.) When the voter—who introduced himself as an “old, Iowa retired farmer”—protested Biden’s comments, insisting that he didn’t say Biden did anything wrong, Biden again shot back. “You said I set up my son to work in an oil company. Isn’t that what you said?” Biden responded. “Get your words straight, Jack.” The former vice president also responded to the voter’s objections to his age—by challenging him to a push-up contest. “I’m not sedentary,” Biden said. “You want to check my shape...let’s do push-ups together, let’s run, let’s do whatever you want to do.”

The argument continued, with Biden appearing to insult the man’s appearance by saying, “But look, fat, here’s the deal.” (Biden adviser Symone D. Sanders disputed this on Twitter, claiming Biden said “facts” instead of “fat.”) The voter responded that “it looks like you don’t have any more backbone than Trump does” and that he wouldn't be voting for Biden, which the vice president did not seem to have a problem with. “You think I’d thought you’d stand up and vote for me?” Biden said. “You’re too old to vote for me.”

The explosive interaction overshadowed Biden’s otherwise smooth day on the campaign trail, as he earned a coveted endorsement from former Secretary of State John Kerry, while highlighting the vulnerabilities that continue to dog his campaign. Though still the front-runner in the Democratic pack, Biden continues to face skepticism over his age, even as 78-year-old Senator Bernie Sanders climbs in the polls after suffering a heart attack. The ongoing Ukraine scandal has also brought new scrutiny of Biden’s tenure as vice president (and a baseless Senate investigation), despite there being no evidence to support that Biden or his son did anything wrong. Gaffe-prone Biden’s quickness to lash out against a voter, too, highlights how his own remarks have become some of his biggest liabilities.

Whether the now-viral Iowa exchange will hurt Biden remains to be seen—but even the Iowa voter who sparred with Biden, who says he supports Elizabeth Warren, doesn’t seem think the moment was a deal-breaker. In an interview with NBC News after his blow-up with Biden, the voter said he would still support Biden in a general election. However bad Biden’s comments may have been, at least he isn’t Donald Trump. “God no,” the voter said when asked if he would support Trump over Biden. “No, he’s a first-class a--hole.”

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