The Democratic nominee's friend Hillary Rosen asked her: "Do you have your strategy?"
"Oh, yeah, I've got my strategy," Clinton replied, according to Rosen. "I have to be warm enough that people like me, tough enough to be commander in chief, deep enough on policy that people know I have an agenda, direct on his faults. Oh, and by the way, I have to be his fact-checker, too."
That's one revelation in "Unprecedented: The Election that Changed Everything," CNN's upcoming book on the 2016 race that comes out December 6. It was written by CNN's Thomas Lake with reporting from Jodi Enda, Susan Baer and CNN's political team.
Clinton's aides filled a suggestion box with ideas for handling Trump ahead of the debate. According to the book, these included: "Drop the names of foreign leaders and challenge him to identify their countries. Fight back if he brought up her husband's womanizing by reminding him of his own. Clinton's aides saw a pattern in Trump's behavior, an inability to let a slight go unreturned, and they thought Clinton could use this trait against him. If she played it just right, provoked him just enough, he might prove her case about his un-presidential temperament."
However, Clinton clearly understood the challenges she personally faced in finding balances between toughness and approachability, as well as depth and directness -- and the need to do it all against a candidate whom fact-checkers have found repeatedly misrepresented the truth on the debate stage.
Trump had mocked Clinton repeatedly for the days she'd spent off the campaign trail, studying policy books and watching Trump stand-in Philippe Reines at the Doral Arrowwood hotel in Rye Brook, New York.
Clinton, meanwhile, bore the burden of already-low favorability ratings, with many Americans' negative views of her baked in after nearly three decades as a lead player on the nation's political stage.
CNN/ORC instant polls showed Clinton won the debates decisively, seemingly giving her fresh momentum headed into the final stretch.
But like so many other pieces of conventional wisdom in 2016, this one disintegrated when voters went to the polls.
Clinton triumphed in an important moment, but Trump won the election.