IMO Trump and Cruz are working together to winnow down the field, especially the GOPe candidates. Hence the focus by Trump on Bush and Walker. If they are successful, then they will go head to head.
Cruz denies the GOPe candidates the ring wing of the GOP, Trump denies the GOPe candidates the center of the GOP (maybe even a little of the left wing). Carson denies the GOPe candidates the left wing of the GOP. Together (Ted, Ben and Trump) all they leave the GOPe candidates are those voters that are loyal to the man or to the mans’ family (Bush). Trump wants Ted and Ben to stay in the race. Ben and Ted are helping Trump win the nomination.