What You See Is What You Get
In all probability, this won't stop the occasional pleas or rumors. After all, Chris Christie keeps getting mentioned as a late candidate, even though he's repeatedly planted land mines on the path to any 2012 candidacy by saying he's not prepared to serve as president. You will also, until the very day someone else nails down the nomination, continue to hear the distant thunder of an alleged 2012 run by another pol who has said "no" a hundred times, Jeb Bush (even though he's now only about the third most powerful Republican politician in Florida, and continues to bear the dynastic name of the president from whose legacy the GOP has been frantically trying to disassociate itself for at least the last five years).
Since the shadowy "GOP establishment" forces who keep lofting up these flaccid trial balloons are presumably not panting for Sarah Palin to leap into the race, they are about out of helium, and really need to focus on the presidential field they actually have.