My guess is that she surprised herself, too. The way she handled the debate, and the response she got from the crowds must have given her confidence. She is a real competitor and now that she has had the chance to measure herself against the competition, the success of her book must have put the taste of it in her mouth. But the year is young, and we still don’t know how things will look in November.
This is much faster than these things normally work, but we have a different communication culture now, and she just might have time to pull it off.