I TOTALLY disagree with your statement about his ablity to explaining things to people of all stripes. Like I said I listen to his radio show for a long time and he always did a GREAT job of doing just that.
Also for your consideration:
http://www.youtube.com/watch?v=J-S3VjofLSM&feature=related
http://www.youtube.com/watch?v=yGBAE0y7iL0&feature=related
http://www.youtube.com/watch?v=fk6PA48uR50
Murtha's boy ended up wiping the floor with his Republican opponent in the May special election here by demagoguing the FAIR tax. I'll grant you that Murtha's average constituents aren't too bright, but neither is your average American voter. Cain needs to learn to relate better to Jane and John Sixpack in the same way that someone like Ronald Reagan or Sarah Palin does.