Burkett is a paroid schizophrenic, and if he feels "sold out" or even "not appreciated enough" then he will turn on those he feels wronged by.
This is exactly what happened with Bush. Burkett started out as a big Bush supporter, but when his paranoid mind began inventing these conspiracy theories of Bush being out to destroy him, he turned on him, and became obsessed with "proving" to the world these conspiracies were real. An augmented sense of self-importance is common with his mental conditions. They typically feel some connection to famous people, and believe they are being stalked, or they are the stalkers. You know the drill.
So if he's sold out by the Democrats, which it seems he already has been, he will quite probably turn on them.
They really messed up big-time getting involved with this nutjob.
In fact, we may discover that Barnes marketed himself and the documents to Rather as a package. Remember, there is still Danny Boy's "unimpeachable source" to be identified.
I can't imagine that Rather was referring to Burkett in this instance. It may be Mapes, but that doesn't ring true -- a journalist wouldn't refer to somebody else in the same organization as a source.
Of all the principles that have so far been identified in this story, only three characters warrant "unimpeachable source" status -- Barnes, Max Cleland and Robin Rather. But, as yet, Robin hasn't actually been connected to the story.
Here's something to chew on. Who fingered Robert Strong as a potential corroborative source? He came into this story out of left field, apparently with only the most tenuous connection to it.
I suggest that, if we knew who volunteered Robert Strong's name to CBS, we'd be one step closer to identifying the "unimpeachable source".