Greg Mankiw calls Joe Biden to account

I guess accountability is not just a punchline to Greg:

As a logical matter, I can think of only four possibilities:

1. Biden knew what he was saying was false.
2. Biden was saying what he believed to be true and somehow got this incorrect idea in his head without talking about the issue with the very talented team of economists working for the new administration.
3. Biden talked to his economic advisers about the issue, and they purposefully misled him into thinking that there was a consensus among economists, even though there isn't.
4. Biden's advisers were themselves mistaken. They expected an overwhelming consensus of support for their fiscal plans and were surprised at the number of prominent economists on the opposite side the issue.

I have no idea which of these hypotheses is correct. I suspect it is either the first or last. But any one of them should make us uneasy about how well the new administration's economic decision making apparatus is working.