All interviews for this book were conducted under the journalist ground rule of “deep background.” This means that all the information could be used but we would not say who provided it.
The book is drawn from hundreds of hours of interviews with more than 200 firsthand participants and witnesses to these events. Nearly all allowed us to tape-record our interviews. When we have attributed exact quotations, thoughts or conclusions to the participants, that information comes from the person, a colleague with direct knowledge, or from government or personal documents, calendars, diaries, emails, meeting notes, transcripts, and other records.
President Trump and President Biden declined to be interviewed for this book.