Announce that you are "looking into" "forming" an "exploratory committee" a la Jeb and Mitt.
A la “Mutt and Jeb”?
“Interest” may take many forms. Perhaps not just for herself, but in other attractive potential candidates.
If Governor Palin REALLY wanted to pull some chains, she could have a high-level meeting with Mitt Romney, much like Jeb Bush recently had.
Then she could turn in “Ernst” to grooming Joni, of Iowa, for the 2020 election.
I do not see Sarah herself actually engaging in a run, any more than, say, Paul Ryan, who has already sort of stepped back from contention.