Is he though? Don't forget his "reconciliation" with Stewart Pearson. He knows they're all playing the game, he probably wouldn't go to the opposition but he will fuck Stewart Fleming up with a mighty vengeance, and he blatantly won't let anything stand in his way, even if meant sparking a leadership contest (though they won't do that cos it's a device already pulled this series).That would be completely out of character, he is a 100% party machine man, even if the machine fucks him he's not going to go over to the opposition, that would be terrible writing.
My bet is that he will come back fuck Fleming up, and the election will be on a knife edge, the episode will end on a cliff hanger with the result not announced until series four, or a special.