This is exactly what I was looking for. In David Plouffe's "Audicity to Win," I learned that the Obama campaign was laser focused on winning delegates, as the Clinton camp were relying on the old fashioned model of winning early, drying up their opponent's fundraising, and forcing them from the field. This is the full account of that strategy, from concept to execution.
Jeff Berman is the only person who could have written "The Magic Number." As the person designated with leading the delegate effort, he takes us behind the scenes as he navigates the bizarre patchwork of rules and regulations across the country to get Barack Obama on the ballot, and to maximize his delegates for the Denver convention, and to fend off challenges that could derail the campaign.
Be sure that's what you're looking for in this book. There may be a good reason why you've never seen the delegate selection process portrayed in film or television. But if you want to learn about this critical component of presidential campaigns, this book is the gold standard. If you want the full story of how the 2008 presidential primary was won, this book has got to be high on your list.
Berman is a great writer, making an arcane subject highly readable and engaging.