I think she and her family made the decision quite recently. Her Indianola speech strongly suggested that she had a platform and a theme for her campaign. Her interaction with the crowd was electrifying. What went wrong?
I think there are two things that impacted her decision. Firstly, much of the vileness that had been directed at her over the last three years resurfaced in the last few weeks as she moved closer to announcing. The McGinniss book and the public attack on Bristol might have been the tipping points. Secondly, I think her legal team pointed out that her enemies could use the FEC and the complexities of American election law to tie her campaign down in legal red tape. Once bitten, twice shy. We may never know, but as Brian Carter at American Thinker pointed out, we are the poorer for her not competing.