Read: How Biden blew it

The ad was harsh and petty, and the Biden campaign didn’t have money to put it anywhere except on Twitter—and thus on reporters’ phones. But that was enough. By the time Buttigieg did his rounds on the Sunday shows the next morning, he was getting asked about his experience at every turn.

To survive long enough to become the unity candidate, Biden first had to be persuaded to rip into his rivals. Between his disappointing finishes in the first three states and his blockbuster victories that followed, the campaign made tweaks like this one. It didn’t overhaul its strategy or upend its structure. What his team did was try to redirect, in specific, targeted ways, a 77-year-old candidate who doesn’t take direction particularly well—and hope the electorate would notice.

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.”

The Biden campaign wasn’t just broken. It was broke. Biden had no money for ads or internal polling, leaving his team to rely on publicly available numbers in order to get a feel for his performance. But it didn’t take a grand master to see that they were about to get checkmated. So, after denying rumors that the campaign planned to leave New Hampshire early, the morning of the primary it did just that. Aides rushed Biden to South Carolina and shoved talking points in front of him about how minority voters—including the black voters who form the backbone of his support—hadn’t been heard from yet. The move helped the speech get prominent TV coverage, which aides thought wouldn’t have been possible if he’d stayed in New Hampshire.

What followed Biden’s early finishes—including a second-place spot in Nevada—was the fastest turnaround from flub to front-runner in modern Democratic politics.

The basics of Biden’s campaign didn’t change. He kept a schedule with only a few events each day. He made new gaffes and generated new questions about whether he can consistently tell the truth.