The conservative Heritage Foundation reacted with bewilderment on Wednesday after Joe Biden claimed that the think tank had condemned the 2017 Trump-GOP tax cuts, saying the former vice president's claim had no basis in reality.

Then, after Biden walked back his comment and instead said the Heritage Foundation has generally sounded the alarm about the national debt, the think tank again called out Biden for falsely implying that it advocated repealing the tax cuts to solve the debt crisis.

The back-and-forth episode, a sort of "Biden claim whack-a-mole," came as verbal gaffes have continued to rock the candidate's campaign, prompting a top aide to call the blunders "a part of his charm."

Speaking at a town hall in Spartanburg, S.C., on Wednesday, Biden remarked, "Even the Heritage Foundation has pointed out that his [Trump's] tax cut did not work."

Adam Michel, a senior policy analyst at the Heritage Foundation and an informal adviser to the White House on the tax law, told Fox News that Biden's comments left him "dumbfounded."

“I have no idea what he’s referring to," Michel said. “It’s clear that the tax cuts have worked and have benefited Americans across the county ... and will continue to benefit them over time.”

Michel added that Biden's remarks were "clearly incorrect," and that "our work has continually shown the tax cuts are working.”

As recently as June, Michel was defending the tax cuts, which slashed the corporate and marginal tax rates, against Democratic presidential candidates' calls for repeal.

"Repealing the 2017 tax cuts would not just hurt the wealthy and corporations," Michel wrote. "It would also leave middle-class Americans tens of thousands of dollars poorer."

In a statement, the Heritage Foundation said the Tax Cuts and Jobs Act "has been one of the strongest and boldest reforms of President Donald Trump’s first term in office."

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Michel added: “The evidence is clear that all Americans are benefiting from the tax cuts. Following the reform, Americans across the country had bigger paychecks and businesses increased investment, wages, and jobs. Average wage growth has been above 3 percent for the last 11 straight months and the lowest wage earners are benefiting from some of the largest wage gains.”

Asked by Fox News later on Wednesday about the Heritage Foundation's criticism of his statement, the former vice president seemingly backtracked and instead focused more generally on the growing national debt.

"The debt is serious," Biden continued. "I think the Heritage Foundation acknowledges that the increase to the debt by $2 trillion is a serious problem."

The think tank has indeed called the national debt a problem that "exposes America to significant dangers." But responding to Biden's latest comments, Heritage Foundation budget expert Romina Boccia said repealing the tax cuts wasn't the best way to fix the national debt.

“You can’t deny the economic benefits of the tax cuts," Boccia said. "The solution to our exploding national debt and deficit is not for Washington to keep more of the money earned by millions of hard-working Americans – it’s for Congress and the White House to get serious about cutting runaway spending.

“Debt exerts a real drag on growth," Boccia continued. "It’s disingenuous to ignore the huge increases in spending that are the real drivers of deficits and debt. We don’t have a revenue problem, we have spending problem. Even after the tax cuts, revenue is up by 3.5 percent, since last year, while spending has grown at nearly twice that rate. Heritage has been clear: we need to address the deficit and debt if we want the benefits from the tax cuts to last and drive long-term economic growth.”

The back-and-forth highlighted the communications failures that have dogged Biden's candidacy so far. Biden's communications director and deputy campaign manager, Kate Bedingfield, went on the offensive on Tuesday and defended her boss amid controversy over some recent verbal gaffes.

Biden raised eyebrows last week when he asked a crowd to "imagine" the assassination of former President Barack Obama while recalling the deaths of political heroes Robert F. Kennedy and Martin Luther King Jr. He also made numerous mistakes while promoting his health care plan, and said he enjoyed being back in Vermont while campaigning in New Hampshire.

“I think the press has to be more careful about applying an unfair standard to Joe Biden than they’re applying to other candidates,” Bedingfield said. “If you listen to what the candidates say all day as they’re out campaigning, they’re out in front of cameras, they’re in front of people, they’re talking all day. Everybody’s going to slip up and misstate a name or a date or a location. It happens all the time.”

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She continued: "People know who he is. They know this is a part of his charm. They understand that, you know, they’re getting it straight from him. It’s not overly packaged. He’s always speaking from his heart. And sure, that means sometimes he’s going to misstate a couple of things. But, frankly, so does every other candidate.”

Fox News' Joseph Wulfsohn contributed to this report.