In Brooklyn headquarters, staff in the 11th-floor nerve center called the Nevada room broke into giddy laughter every time the increasingly desperate Rubio repeated himself. But back in Manchester, the new reality hit Clinton’s inner circle like a ton of bricks—there might be no one left who could stop Donald Trump from clinching the Republican nomination.

“When Rubio got taken out in New Hampshire on the debate stage, that was a moment when I said, ‘OK, this looks like it,’” said former New Hampshire Democratic Party Chair Kathy Sullivan. “He was the golden child at that point, and then was just destroyed.”

“That’s when I realized that there was something bigger going on,” added one of Clinton’s longtime friends and advisers who remembers watching in disbelief, feeling in the moment that the ground was shifting underneath the campaign. Trump “is a master manipulator and a master of the counterintuitive. He knows exactly how to get things done. It’s disgusting to watch. But it’s effective.”

Even with that view emerging so early in the contest (it would be 16 more weeks before Trump clinched his party’s nomination), Clinton’s team would struggle in the ensuing months to land on a strategy that would stick. Within days of that February GOP debate, Clinton’s aides started considering how to redraw the battleground map it had been relying on for well over a year, assessing Colorado’s and Virginia’s swing-state status and re-running the numbers on suburban white women and young Latinos. They would direct the Democrat to try out, and ditch, one campaign slogan after another. And as she finally wriggled out of the primary to face Trump, the strategy was still evolving, producing dramatic tactical shifts — from embracing disaffected Republicans to firing up liberals, from previewing an uplifting closing stretch to savaging Trump with an unprecedented television ad barrage.