Cruz is viewed by a large majority of Republicans as being completely untrustworthy and likely insane.
If you have any questions why, please review the “naming Carly Fiorina VP” fiasco, and remember that it happened AFTER Trump was already incontrovertibly the presumptive nominee.
Have you ever wondered why he thought that could even be a plausible thing to do? He knew about the so-called “dossier,” they all did, that’s the only explanation that makes sense. That thing had been shopped around for the better part of 2016 and nobody would bite as far as publishing it, but in hindsight just look at the odd behavior on the part of both Republicans and Democrats, all the “never be President” garbage. That whole thing stinks on ice and now is the time to get to the bottom of it since we have a special prosecutor looking into foreign election interference which this certainly was.