The Lead Read: 'Days of Fire' author on the 'Shakespearean evolution' of the Bush-Cheney relationship

The new book "Days of Fire: Bush and Cheney in the White House" explores the relationship between former President George W. Bush and his vice president, Dick Cheney.

There has been a lot of speculation about what drove Bush and Cheney apart.

"I think it begins with Iraq," said Peter Baker, White House correspondent for The New York Times and author of the book. "The war starts to go badly, there are no weapons there, and Bush begins looking at a second term. He's got to make a case to the American public. Cheney offers to drop off the ticket."

Bush keeps Cheney on the ticket, but begins thinking about how he can begin to reshape his administration.

"What do we have to do for a second term? More diplomacy, less bellicosity. That takes him away from Cheney," said Baker.

Afterward, a series of events further drive the two men apart. Bush didn't pardon Cheney's top aide, Scooter Libby, a decision Cheney still publicly criticizes. The former president also began to rely more on former Secretary of State Condoleezza Rice, elevating her to begin moving in a different direction on the international stage. There was more diplomacy with North Korea, Syria, Iran, a move toward Middle East Peace – things that Cheney found troubling, said Baker.

"He believes that they are beginning to drift away from the principles they shared in the first term. So by the end, they're on opposite sides of all sorts of issues, not just those, but also climate change, gay rights, gun rights, auto bailout, so on," said Baker.

"It's a very dramatic evolution, almost a Shakespearean evolution over eight years," said Baker.

For more of our interview with author Peter Baker, check out the video above.