Regarding the Republicans not trusting Bush to testify without his handler. They aren't even trying to maintain the fiction that he's his own man.

"A top Republican strategist dubbed the legal document striking the unusual deal “the Wizard of Oz letter” because it strips away the myth that Bush is in charge. Until now, it’s been all speculation about Vice President Cheney’s influence. With the revelation of the tandem testimony, nobody with a straight face can deny Cheney is a co-president or worse, the puppeteer who pulls Bush’s strings.

"Aside from being fodder for the late-night comics, the arrangement confirms Bush’s inability to articulate anything without a script--or a tutor by his side. There’s a reason lawyers don’t take testimony in groups. The whole idea is to get individual recollections and then compare stories to uncover contradictions. Try thinking about it this way: can anyone imagine Bush’s father in a similar situation bringing his vice president? (For those who need a refresher course, the elder Bush was a rocket scientist compared to his son, and the vice president was Dan Quayle.)"