In Confessions of a White House Ghostwriter: Five Presidents and Other Political Adventures, former presidential speechwriter (for Eisenhower, Nixon, Ford, and Reagan) James C. Humes offers a tremendous insight into the decision-making processs: "Sometimes -- even if the general details of a legislation message have been hammered out -- unagreed matters remain because of fights between competing departments. As the various drafts of the proposed message are relayed to various cabinet heads for approval, one cabinet secretary knocks out one word or item and his rival puts it back in. A change goes in -- then it's taken out ... The hours pass from late night into the wee hours of the next day, when the president is scheduled to deliver the message. Finally, the department heads go to bed and final decision is left to the (speech)writer -- hence the 3 a.m. president."
"I remember one message on mass transit by President Nixon. The bone of contention was funding," from either the gasoline tax or general revenues. "I had to decide. I chose general revenues. Strangely, my decision drew no backlash. Everyone assumed the president had made the decision."