He won't defect, ever. I'm not sure if it was woodward or burnstein, but one of them noted comments by alot of people around Powell, that he always looks to shore up his "moderate credentials" and does so quite often at the presidents expense, to the point where some people aren't even sure what he believes. He went to some function in NYC and basically made alot of jokes to that effect that he wants to be known as a moderate. When he was a general under clinton, he was thought of by them as being very hard conservative, so I think the WP writers have him pegged right, and they like him.
The whole thing between Powell and Clark is just personal stuff. It also doesn't help that alot of people at the top, think that Clark is a mad man, on CNN he's scary with his always "seeking to expand the conflict to global proportions". In the balkans he ordered the british, who refused, to bomb russian ships, its also widely rumored that he intentionally bombed the chinese embassy, and was even giving orders to "secure areas outside the present zone of conflict" (i.e. go into other neighboring countries not involved). He sees himself as wanting to be like a Patton or Ike. His whole search for a greater glory, the lefty's are absolute idiots with this guy, he's not one of them, he's not one of us either, he's delusional in his whims without care of ideology.