It was the Cruz campaign that originally contracted with them - that's why Bannon was involved, it was when Mercer was still backing Cruz
www.washingtonpost.com/politics/cruz-campaign-credits-psychological-data-and-analytics-for-its-rising-success/2015/12/13/4cb0baf8-9dc5-11e5-bce4-708fe33e3288_story.html