NEW YORK — “So, let’s talk about last night’s debate, because I know it’s on your minds,” Jill Biden said. The living room of the Greenwich Village brownstone fell silent. The first lady, poised in a polka dot dress and a pair of pink stilettos, stood behind a lectern, her lips spread into a half-smile. The nearly 60 attendees at that afternoon’s fundraiser, gripping the melted remnants of their Aperol Spritzes, stared back at her. [cut] To his wife of 47 years, it was no reason to panic. “I said, ‘Look, Joe, we are not going to let 90 minutes...