I could see it only under these circumstances:
Romney gets the GOP nomination. The Tea Party then decides they’ve had enough and they become more focused on taking out the backstabbing GOP Beltway Establishment than on taking out Obama. So they create the American Conservative Party and Sarah heads their ticket next November. The GOP comes in third and essentially goes out of business.
Obama eeks into a second term in a three-way split, but with opposition majorities in both houses he is so incredibly weakened it becomes a moot point. The new Conservative Party becomes dominant and takes the White House in 2016.
Ballot access:
Each state has its own ballot access laws to determine who may appear on ballots and who may not.
3rd Parties cannot get on the ballot in time.