Biden at first resisted going negative, aides say—he doesn’t like attacking fellow Democrats. But after a fourth-place finish in Iowa, he went after Bernie Sanders, whom he genuinely likes and had resisted taking on in the debates, by smacking down socialism every chance he got. And although he’d been touched by Buttigieg’s defense of his family during the impeachment fight—and had come to see shades of his late son in the young mayor—he started attacking his moderate rival. He had no choice, his closest aides told him. This was a Do you actually want to be president? moment.

“He did not love taking a sharp swing at another Democrat,” Kate Bedingfield, Biden’s deputy campaign manager, told me on Wednesday, recalling the conversation she’d had with him after the campaign decided to release the Buttigieg video. “He did not love taking it at Pete, whom he likes and respects. But he also understood and knew it was necessary to interrupt the narrative and shift some of the dynamic in the race, which he knew desperately needed to happen.”