The fact remains, Palin- in her OWN words on more than one occasion- has said she hasn't found someone to support. Whether that changes remains to be seen.
It’s not a guess. That’s why ALL the words were important. She had already started the next sentence (about the field being “impressive”, and she repeated that start of the sentence after Kelly’s interruption, which shows she was still finishing her previous thoughts, not changing the answer based on Kelly’s question.
I agree with what you say in this comment: “She wasn’t anyone she could put her heart and soul behind as a candidate”. But that’s different than saying she couldn’t support any of the candidates.
If someone asked me, I would answer the question the same way. I haven’t yet decided I can support any of the candidates with my whole heart and soul. But it would be foolish to interpret that as saying I COULDN’T support any of the candidates fully. Just that I haven’t decided yet if I can. I’m still evaluating, just as Sarah Palin said she was still watching and deciding.