Roger Douglas won't just be running for election again - ACT wants him in Cabinet. National professes reluctance, of course, but if the numbers go ACT's way, they might not have much choice about it (and despite Key's statement, the prospect of being "forced" by a coalition partner to restart the Revolution and complete Douglas' "unfinished business" will not be unwelcome to many in National).
Fortunately, Douglas is so reviled that the prospect of his return should be self-defeating. But I'm sure there'll be people wanting to help it along with a "a vote for National is a vote for Douglas" campaign.
(Meanwhile, this should be a reminder to everyone that, contra Buffy, a stake is not enough. You also need to sever the head and put holy wafers in the mouth. Otherwise the bastards just keep coming back...)