Stuart Stevens, Mitt Romney’s top strategist, knew his candidate’s convention speech needed a memorable mix of loft and grace if he was going to bound out of Tampa with an authentic chance to win the presidency. So Stevens, bypassing the speechwriting staff at the campaign’s Boston headquarters, assigned the sensitive task of drafting it to Peter Wehner, a veteran of the last three Republican White Houses and one of the party’s smarter wordsmiths. Not a word Wehner wrote was ever spoken. Stevens junked the entire thing, setting off a chaotic, eight-day scramble that would produce an hour of prime-time problems...