You’r looking at it wrong, but in the standard GOPe way.
Trump/Cruz would get the base out like we haven’t seen since Reagan.
(And yes, Cruz would solidify the Christian/Evangelical vote for Trump.)
Trump will get the base and LOTS OF OTHERS. Cruz adds NOTHING and loses opportunity to enlarge the base. Cruz you lose. Who would help Trump? That is the 2016 question of the spring. None of the other candidates will. Maybe another Republican governor?