 Last night's debate was a watershed on both counts. The debate was not just a catastrophe for President Biden and boy, oy, was it ever. It was more than that. It was a catastrophe for an entire class of experts, journalists and pundits who have since 2020 insisted that Biden was sharp as a tack on top of his game, basically doing handstands while peppering his staff with tough questions about care for migrant children and aid to Ukraine.