Since none of us has access to her grand plan we really don't know how this move fits. Fun to speculate, but too easy to come to the wrong conclusion.
Well, part of a candidates “Plan” is to keep the opposition guessing what they are up to...not revealing your hand too early in the game...also to divert attention while you shuffle your cards when and if needed. Palin’s done outstanding in that respect.
......and what a fun game to watch!