Murphy was a casualty of the MSNBC anchor wars:

Also on Wednesday, the New York Post reported that Olbermann was an obstacle in allowing McCain adviser-turned-NBC political analyst Mike Murphy to get on the air during the convention. Murphy was bumped from Monday’s convention coverage due to “technical difficulties,” the Post reported. He also didn’t appear on Tuesday. 

“I’m told I’ll be on the air tonight,” Murphy said, when reached by phone Wednesday. 

I guess he finally got on:

The greatness of McCain is no cynicism, and this is cynical.

Congratulations, Mike.